As the OP implies, there's a limited amount of space for RPGs so only the finest examples should stay. Finest examples fo doing different, often contradictory things right. Also, I don't find it right including D&D-related stuff since one can just sit and play a D&D campaign with a better story than what Bioware ever came up with written by your co-players. OP you didn't think about non-computer RPGs aren't you?
And this is what I'm coming from while listing these:
1. Fallout 2: RP 2.3.3 - the client mainly for Fallout: Nevada and possibly for F 1.5: Resurrection but on its own merits has some fine moments and was fine tuned by fans. This applies to a lot of RPGs actually, did you consider fan made patches and mods that often contain games within said 5 games OP? RPGs don't exist in a vacuum, they're always under fans sight
2. Arcanum multiverse edition - does core concept of an open-world RPG better than Fallout and has greater length filled with glorious stuff
3. 7.62+Hard life - a fine example of RTwP combat-centric game. You'll need at least
one good of those and there's nothing better than a russian game for this
4. Silent Storm - because you need at least
one good turn-based game and you know the rest from point 3
5. Vampire the Masqurade: Bloodlines unofficial patch 10+CQM 4.1 - I like ARPGs with decent writing. I don't need other explanation for this one to exist
(6) The Witcher 3 Enhanced Edition/Cyberpunk 2077
Quescarza Ellaine Edition(/Fallout New Vegas Ultimate Edition+2019/2020/2077/4.000.000.000+modlist
+sexout) - Okay, this one is in precarious situation, it's not like ths p.6 is even needed. Usually sequels in such situations as game apocalypse are a no-no. But Twitcher 3 has more in common with the books than previous games and you'd need at least one modern AAA RPG and they all are shit not worth saving it has decent enough worldbuilding. CP2077 is not a sequel to anything but PnP timeline which is potentially better for the spot. It also can potentially omit F:NV, setting wise post-apoc is covered by F2.
SkyrimEnderal+DLC is a potential candidate since there's no Gothic-like AAA on the list yet. Personally I want to include Космические Рейнджеры 2(reviewed by Vince himself) in the list but it's not an RPG and the list would make it russian-centric. It's almost makes it like no one else liked computer RPGs... Wait.
To make up for the loss I chose games that include an editor with them to not just replay and study but create new stuff on top of the base five games. This one culls CD Projekt RED efforts unless they comply and release an SDK under such circumstances.