I'd say the 60s got the Daleks just right.
They were a force to be reckoned with, a galactic threat that outshone all others. Even when used for comedy (The Chase), their appearance was a big deal. As I've stated before, I have a low opinion of the Pertwee Dalek stories. I think the fact that Letts/Pertwee didn't like them is very obvious. They were squeezed into "Day of the Daleks" (a totally unrelated script from Louis Marks), then Terry Nation came back and essentially rewrote "The Daleks" for season 10. And then he crapped out "Death to the Daleks" with the most basic action-adventure tropes. All of their appearances felt cheap and obligatory to me, like Letts wanted to piggyback off of residual Dalekmania to boost the show.
"Genesis of the Daleks" was fantastic, because Hinchcliffe and Holmes had a ridiculously high level of quality control. It's kind of an outlier. "Destiny" was another cheap entry without an ounce of creativity or effort. They dragged some old crappy Dalek costumes out to the quarry and wobbled about with them to build hype for the season. The combination of Nation and Adams is like steak and ice cream. Just thinking about his goofy humour intermixed with Nation's grit in those crappy plastic overlit sets makes me nauseous. Gooderson's Davros warbling his poor imitation of Wisher under that dusty mask is the cherry on top.
The 80s Dalek stories are alright. I don't have any special love for any of them, but they're all watchable.
Sorry but I disagree strongly with those two statements.
I do like the 60s Dalek stories and they did plenty of interesting things that set the standard for the monsters to come for decades, like their xenophobia, time travel, feud with the Doctor, basics of their lore like Skaro and the Thals, being created by an atomic war etc. However they did NOT establish them as a big intergalactic threat. The Pertwee era deserves the credit for that and arguably the 70s as a whole including Destiny is the only time they come over as an intergalactic threat. Let's go through it.
In their first story they are a near extinct race on a remote planet who get defeated by farmers.
In their second they have conquered the earth, but that's it. No mention of a Dalek empire. It's also implied they want to steal the earth to live on it because Skaro is dead. That is their motivation in the Cushing movie.
In the Chase they are just after the Doctor (for foiling their invasion of earth.) They do have a run in with Aridians, but that comes to nothing. They don't conquer the entire planet, and only threaten one group of them because they house the Doctor, and are actually quite merciful by Dalek standards in that they let the Aridians go after the Doctor and co escape, rather than say send a message to Dalek command to conquer the planet.
In Daleks Masterplan we finally hear that they have other colonies, but even then their main aim is still to conquer the earth and they need the help of dozens of other aliens to do that in building the Time destructor. Also at no point are those other colonies said to have been populated by intelligent creatures that they have conquered, and the Varga's are said to have been from Skaro IE not another race from another planet they have subjugated.
In Power they are dealing with a far flung earth colony and that's it.
In Evil their whole plan is to learn about humanity because humanity has always defeated them, and their plan is once again just to deal with earth. Also a civil war on their home planet is enough for the Doctor to believe that they have been wiped out showing they clearly don't have an empire.
Also in Space Museum a Dalek sits in the Morok's hall of greatest triumphs showing they got their arses kicked by those stupid double eyebrow aliens.
Really in the 60s, the Daleks are just another alien race that is primarily concerned with the earth and humanity. They're like the Martians from War of the Worlds, and Mekon and the Treens in Dan Dare in that respect. (Both of whom BTW where their biggest inspiration.) Indeed in terms of power there is nothing to suggest they are greater than the Cybermen or the Ice Warriors. The Time Lords haven't even heard of them in the War Games and dismiss them along with the other monsters as entirely irrelevant at first.
The Pertwee era is what establishes them as an intergalactic threat and puts them ahead of other villains in the series too in terms of power.
In Day of the Daleks, okay its still earth they have conquered (to be fair as it is a show made by and for humans, then yeah we are going to be at the centre of it.) Still in Day it is mentioned that they have a vast empire and have conquered hundreds of other worlds, and that the earth is only valued because it has lots of resources and they've turned it into a big factory to help conquer other worlds, rather than because humans are special and their greatest enemies, like in Evil of the Daleks or even Daleks Masterplan. We also see another race they have under their thumbs, the Ogrons who have been broken to such an extent they basically can't think for themselves without the Daleks. (The fact that they are giant, super strong monsters who can kill humans with one punch further shows how powerful the Daleks are.)
In Frontier in Space they plan to destroy both the earth and Draconian empires, whilst the Master is their servant and has to watch himself around them.
In Planet of the Daleks meanwhile, we see another world under their rule that was conquered in the same way as earth. The Spirodons unlike the Vargas are intelligent creatures with their own civilisation who are capable of being good and evil just like us (with Wesker being one of the most noble bastards in the entire show.) What's worse is that this planet Spirodon isn't freed at the end of the story. It's a scary idea that there are hundreds of worlds like Spirodon, that haven't been so lucky. In this dynamic, humanity aren't the greatest enemies of the Daleks, it's more that because the Doctor has history with us, and perhaps we are in a more remote corner of the galaxy, where if the Daleks ruling it are destroyed the empire won't know right away, then he was able to free us, but sadly hundreds of other worlds that are in the centre of their empire, or perhaps in other remote corners he's never even travelled near won't be so lucky. For every three planet's like earth he saves, there's probably 10 more lik Spirodons. Also if you include both stories together, we have humanity, the Draconians, the Thals and the Time Lords all uniting to stop the Daleks working on their own, and I do mean the Time Lords overall, not just the Doctor. Planet's the first story where the Time Lords take an interest in the Daleks and view them as a potential threat they need to step in and deal with by sending the Doctor after their ship, which arguably paves the way for Genesis and if you like New Who, with the time war itself.
Also the fact that the Thals don't know earth exists, despite it being an intergalactic power, shows you how large the Dalek empire is and how big a threat they pose that life forms from different edges of the galaxy are just as much of a threat to them. The ending also unlike a lot of 60s and 00s stories, doesn't end with them being completely destroyed. Instead it's portrayed as you can stop this one plan, but the Daleks will always have another up their sleeves, and even if you free a few planets there will always be more under their rule. Basically you cannot completely destroy them.
Death meanwhile actually shows them conquering another world for the first time on screen. Unlike Aridius where they only shoot and threaten a few people to get to the Doctor, Death shows them slaughter dozens, actually round aliens up into cages and camps, work them like slaves, use terror tactics against their population etc, even when they suffer from a power drain too!
Meanwhile let's look at later eras? You won't see them conquer any other alien races at all in the 80s, and in fact off screen they get their arses kicked by the Movellans. In the entire 21st century other than a flashback in Day of the Doctor, they are only ever shown in combat with humans. (Even the Cybermen they bitchslap come from modern day earth.) Journey's end I'll give you does make them a big deal by having them steal other planets threaten the multiverse, but even then we never see the other worlds they have conquered which is a shame. I would have loved to have seen some aliens in the Dalek testing area, or the planned battle with the Shadow Proclamation, but ultimately it still feels very earth centric, with the Daleks even calling ruling the earth their ultimate destiny.
To be fair there are some other Daleks fighting aliens moments in New Who, but as we've been over they all involve them getting their arses kicked, like the water girl, or Hellbent, or the flux eating them up.
Genesis meanwhile also reveals that they will eventually destroy all other life forms in a dark vision of the future and shows the Time Lords being willing to break their most important laws, whilst Destiny similarly shows them in combat with another race of aliens (the Movellans) and also has a Dalek death camp where there are aliens from all over the universe, not just earth further showing what a large scale threat they are.
Also as for undermining them? Bullshit, the 70s stories establish them as a legit threat again more so than the 60s stories.
In Day of the Daleks, we see how they completely rule the earth to the point where changing history is the only way humanity can stop them. We also have them brutally torture the Doctor almost to death. have a race of giant ape men reduced to their pets, and we see how powerful they are physically. Just a few Daleks plow their way through UNIT troops whose weapons don't even take down one. This is UNIT who by this stage have slaughtered scores of Cybermen, Autons, Silurians etc. Also they explicitly make out that only one type of explosive (created from the Daleks own formula) can destroy them, and I might add anyone who does manage to take one down, dies in the process too because the explosives are too strong. I'll be honest the Daleks in Day are far more formidable than those in most other classic stories. Compare them to those in say Remembrance, Resurrection, Evil and Daleks Masterplan for instance? In Remembrance an ordinary 1960s earth rocket can blow them up, and one of them can't take on Ace, a teenager with an electric bat, without calling for reinforcements. (I LOVE that moment to be clear, Sophie is badass jumping through the window, but yeah it's a bit demeaning to the Daleks.) In Resurrection they got blown up by ordinary 1980s earth guns, and explode when falling out a window, in Evil similarly kicking one off of a railing that's about 20 feet high onto a wooden floor (that fall might not even kill a human) breaks one in half, whilst Ancient Egyptians with stones take one down in Masterplan (and it's quite funny when they do. "HEEEEELP HEEEEEELP".)
Day also takes us deep into how cruel they can be, the way they work their slaves to death, including women and children, and the relationship between the Controller and the Daleks is fascinating and to be honest the best example of the devious human working with the Daleks trope apart from Davros. Mavic Chen is fun, but he is a bit more of a cartoon badguy who just wants power (and is also stupid for thinking he has it.) Maxtible is similarly just a greedy dick, whilst Waterfield though a good character, is just a victim, whilst Lesterson is duped by them and the goes insane. Meanwhile Lytton is nothing more than a lacky, and Radcliff again it's fascinating watching him be drawn in by their vile ideology due to his own prejudices and then getting treated as inferior scum the way he did others, but other than that he doesn't have much to do after the little girl is unmasked. Mike is a great character meanwhile and a more complex and interesting look into bigotry and how sadly good people can be sucked in. However even then he doesn't get much interaction with the Daleks other than one bit that's sadly a bit cringe "You said it mate." And to be fair in his own words "He didn't know it was the Daleks sir."
The Controller however is one who does keep you guessing what his true motives are throughout the story, who genuinely does seem to believe in them through a combination of trauma and privilege, who can seem earnest in how shocked he is when they go too far, but also seems to enjoy being able to bully people thanks to his position as their head toady. You hate him and pity him at different points, and in the end his redemption not only make sense, but it and his final defiance of them are a brilliant moment of the Daleks being hoist by their own petard and cruelty.
Planet of the Daleks meanwhile shows how they have weapons, such as the plague that can destroy the surface of an entire planet. In Daleks Masterplan they could only reach that level of power through working with 12 other aliens over several decades to build the Time Destructor. We also see how a Dalek gun can melt an entire spaceship, have a Dalek flying on screen for the first time, have their master plan be to conquer an entire galaxy rather than just the earth. Also I might add it is in fact the only Dalek story where humans aren't their enemies at all! Other than Jo Grant, it's all aliens they are fighting, with earth again just being one of hundreds of worlds they are capable of conquering.
Death to the Daleks meanwhile again shows them conquer a race of dangerous savages (with a power drain.) It also shows how much ahead of the humans they are. Humans stranded on the planet for weeks, weren't able to take down one Exxilon, were living in fear and had no idea what was causing the power drain. The Daleks meanwhile sort it out in about half an hour and have the planet under their thumb in that time too. We also see how they are equal to the Doctor in that they are the only other life forms that are able to make their way through the Exxilon city, and the monsters are also sneaky and crafty in the way they trick the Doctor and the humans as to what their true motives are and actually manage to get away with the paranium an would have destroyed the Doctor had it not been for a treacherous human. )
Also I might add that it's the Pertwee era that establishes them as the villains the Doctor hates more than any other. Pertwee actively enjoys killing them or watching them be destroyed! Pertwee is normally one of the most upstanding Doctors and tries to reason with his enemies, even the Master, but when it is the Daleks he enjoys watching them die. Again these are things we see in Eccelston and Matt Smith and Peter Capaldi in the revival and even Sylvester McCoy who seemed to enjoy killing the black Dalek.
I don't believe for a second that Pertwee phoned it in in any of his Dalek stories. He is brilliant in all three, in fact I'd say Day of the Daleks is his best performance in the role after Inferno. His scenes with the Controller are a highlight. "You sir are a traitor! You're a Quisling!" A part of me is wondering if he did hate the Daleks as much as he claimed, only because hilariously enough he seemed to do more publicity shots with them than any other Doctor I can think of, and I'm not talking about during the show but after. FFS almost every public event has him beside a Dalek LMAO. Also given how much control Pertwee had over his era, in terms of the monsters that were featured and the type of companion he was working with, I find it hard to believe he'd be quite so flooded with Dalek stories otherwise? I mean don't get me wrong, I don't doubt he meant what he said that he found them tricky and annoying to work with because of their limited movement and preferred the half mask villains, but I think his hatred of them was just him being an entertainer as it was always a hilarious story to tell. Still even if that was true, Pertwee was 100 professional and never phoned it in. He also said the Primords in Inferno were his least favourite monsters because of how stupid they looked, yet he still treated them like they were the scariest . He was a Peter Cushing in that respect.
Meanwhile I don't know where you heard it that Barry Letts hated the Daleks? He loved them! In fact it was his passion for the Daleks that convinced Bob Holmes to do Genesis, as he felt that if Barry was that enthusiastic about them there must be something in it. Sadly Holmes did not like Terry Nation. Some people think he didn't include the Daleks to spite Nation, as when they met at a party, Nation boasted about how the show needed them and Holmes wanted to prove him wrong. He also is believed to have turned down being the script editor for B7 due to his dislike of Nation too. Still at least Holmes did write for it showing maybe he overcame that dislike eventually, but certainly not at the time of Genesis.
Holmes and Hinchcliff had very little to do with Genesis meanwhile. Sorry but it annoys me that people try and give them the credit for that instead of Nation (like Neil Perryman.) To start with it's obviously a Nation script, and second Holmes due to his snobbery about the Daleks did very little work on it. Terrance Dicks, Barry Letts and even Philip Hinchcliff all said as much that Genesis went through very little rewrites when compared to other scripts.
(Compare it with Revenge where Holmes was forced to do the rewrites and because he hated the Cybermen in a similar fashion, it shows.)
Honestly for me the 70s is the best era for the Daleks, with the best individual story, and the only time they are a legit intergalactic threat. I'd go as far as to say that the Pertwee Dalek stories suffer from Lost in Space syndrome LOL, in that they were ahead of their time and extremely influential, but haven't been vindicated yet and still get trashed for things that other stories did. Like Day of the Daleks, everybody goes on about how lame it is because there are only a few Daleks, then goes onto praise Dalek for showing how only one Dalek can slaughter hundreds of people?
(I might add the Pertwee era's influence even goes beyond DW as Day of the Daleks directly inspired the classic X-Men story Days of Future Past, which some people believe inspired Terminator as well.)
Of course that said obviously the Pertwee era stories do have their faults. Planet is a bit derivative of the first story, though even then I think this has been exaggerated. For instance, Journey's End is far more derivative of Parting of the Ways, and Weng Chang is probably as derivative of the Time Warrior. Also I do think that some of the Pertwee Dalek stories were limited by Barry Lett's more family friendly approach. I understand why he did it, but honestly Dalek stories for me at least should be darker. Planet of the Daleks was to have ended with the Thals all being killed by the Daleks, which honestly I think would have really helped the story stand out and made the Daleks seem more formidable, but Letts was worried that would be too horrifying.
Still overall the Pertwee era Dalek stories are very, very underrated.