I feel like the emphasis on long form drama is a mistake for the idea of "cream of the crop" television.
I actually strongly agree.
I won't derail the thread with a detailed discussion but it's not just nostalgia or something, but I do think TV has kind of gone down a dead end by only applying big budgets and serious writing to long-form shows, and it's part of why YouTube and so on have been so successful, and why a lot of people, even much younger people, are watching/re-watching TV shows which ended their runs 10+ years ago (and also why anime has become increasingly popular, which tells often engaging stories in 20-minute chunks, though it is experiencing issues of its own), because they're providing something modern TV increasingly rarely does. That's not to say long-form stuff doesn't succeed, but its prevalence is I think disproportionate to its actual value and worth. If there was a DS9 or Buffy today that wasn't just a revival, it'd almost certainly be animated and underbudgeted and allowed to run for like, at most 2 seasons. Hell, a Supernatural today would get the same treatment and that ran for 15 years!
let's contrast some films. In one corner, we films of high regard for their cinematic quality like There Will Be Blood and No Country For Old Men.
I enjoy re-watching every few years because they scratch a certain itch (in this case, mega-disaster), but I don't see as being all that well made, 2012 or Deep Impact (not quite "comfort" films, but certainly entertaining).
I find this an interesting juxtaposition, because personally, whilst
No Country for Old Men is basically un-re-watchable due to Javier Bardem's insanely chilling performance, I found
There Will Be Blood to be almost jolly in its sheer insanity (maybe I just can't take that entire era of human history very seriously) and have watched it a few times, and I find
Deep Impact to be 100% impossible to rewatch because it's so horrific and worse, has a sort of despicable (to me personally) saccharine tone and precious-ness which just seems inappropriate with a lot of the stuff it brings up. It's a much better movie than
Armageddon but if forced to re-watch one I'd pick Armageddon every time.
Anyway lists - very partial and bear in mind I haven't had my coffee yet, let alone my ritalin!
TV:
Buffy S1-5, S7, Angel
Deep Space Nine
Law & Order S1-12-ish (not exploitative and laughably preachy SVU or the rest, or later, "modern copaganda"-tainted L&O - early L&O is often copaganda, but it's copaganda from a different, better, era) - would/will likely replace with HLotS if that ever becomes viewable again (I know they're working on it).
For All Mankind
Slow Horses
Drag Race (if Taskmaster gets in, and I agree it does, this does! Both are clearly a cut above most "reality" shows, and oddly, share certain similarities)
Line of Duty
Movies:
Master and Commander - Not sure how this hasn't already been mentioned, it is absolute archetype of what
@Mercurius is describing, both extremely watchable and engaging and extremely high quality - very re-watchable too for some reason!
Aliens
Conan The Barbarian (1981) - Honestly an incredible movie and the soundtrack alone makes it easy to rewatch
The Last Unicorn
Die Hard
Hard Boiled (1993)
LA Confidential (I love the book but I actually think the movie kind of does a better job presenting a lot of the concepts to a general audience)
God this is looking very '80s/'90s, how old of me, I know there's a lot of more recent stuff I should add, will try and remember to do so later.
Honorable Mentions: Grave of the Fireflies, 2001 A Space Odyssey, My Cousin Vinny, Citizen Cane, Spirited Away, Witness For The Prosecution, Hereditary, Shawshank Redemption
(I wish I could put Kimmy on this list, if it was the Pinot Noir show I probably could...)