Puzzle Pirates, frankly. Made by people who knew what they were doing, were extremely talented, independent, although eventually tried to hook onto Sega as publisher, almost killed the game and then re-purchased the game from Sega to continue as "re-indie" devs. Still going to this day with a stable player base of a few hundred. The game itself is very clearly hand-crafted and every one of the (few) developers left their mark on it. Feels completed and polished.

A videogame that was made with complete love and devotion to the medium, made with talent and sincerity, and is a pinnacle of everything it stands, something that will stand the test of time...

And nobody mentioned Stardew Valley? I spent too long looking for it and didn't find a single mention of it. Absolute mastery of its genre, an incredible amount of dedication spent by the developer listening to the fans, and I can't imagine it not still holding up 10 years from now, or even 20 years from now.

Baldur's Gate 3 is great, I love it, but there were so many performance issues with the game even with top tier hardware, and the game was borderline unplayable for others due to these issues. I have a little bias since my save didn't sync across devices with the steam cloud and I have to start all over. Love the game, but I just can't believe Stardew Valley isn't even mentioned.

Baldur's Gate 3

As far as labors of love go, Stardew Valley is probably the most current example. People paid for this thing years ago, but Concerned Ape keeps adding new features anyway. The retro graphics give this thing a timeless quality out of the box, so it already looks "dated" - this hasn't stopped the robust player community around it. We'll probably see this game stay relevant for a long time.

Dwarf Fortress.

Mass Effect. I know some will disagree, the third game has a lot of glaring issues, and EA really fucked up the ending, but as far as a fully fleshed out story and universe with a multitude of unique and independently structured species, characters, and cultures I think it’s one of the best. The writing and possible story outcomes and decisions that vastly and permanently affect the story from the first to the third game are insane.

Neither of these are popular enough to be on the scale of LoTR, but in terms of atmosphere and detail:

Hollow Knight - my absolute favorite thing about it is each NPC has its own voiced language recorded, babbling in the background as you read the dialogue.

Subnautica (the first one) - shitting myself with each new experience is something I'll always cherish. Highly recommend just playing without looking into the gameplay or plot. Has elements of exploring, resource gathering, base building, psychological horror (not graphic, just tense scenarios), sneaking.

The first Halo trilogy takes the cake for me

Enderal 🥰

Outer Wilds is this game.

Cold Waters if you're hankering for some hot sub on sub action.

Ocarina of Time. I'm biased because of nostalgia, but I genuinely think it's the best game ever created. It took everything that was great about the SNES classic A Link To the Past, brought it into 3D as an early N64 game, and improved literally everything. The atmosphere, the gameplay, the story, the time mechanic, the music... It's not perfect, in fact these days it's trivial to break many things in it with glitches, but I think it's absolutely the best.

Half life and half life 2

Minecraft

☼Dwarf Fortress☼

Half-life.

Terraria! That game is great and aged like fine wine

FALLOUT NEW VEGAS! (Side note) Oh boy, a new list of games to play as I scroll through these comments.

World of Warcraft, at least for the first 3 expansions. I think the people that made it back then were utterly devoted to the story and gameplay, as were the players. I'll remember playing that until I die, so many memories.

Downvote away.

Surprised no-one pitched Elite:Dangerous. Certainly a labour of love to begin with, incredibly talented sound design, first space sim to VR, truly devoted to the original material... Still going pretty strong (had a few weak years) with updates (only 2 DLC-ish major updates of which were paid) a decade later...

Clair obscur

Hades

Factorio

Terraria, amazing game that is still supported to this day, best 5€ I've spend on a game.

Without a doubt the Witcher games, and Baldur's Gate 3. Probably Dragon Age too, but I haven't played those.

Undertale and Deltarune.

Dwarf Fortress.

Ultima 1-7 and 8 partially.

Prumbably the Morrowind game

There are too many to mention.

MechWarrior 2
Dragon Age: Origins
Daggerfall
Clair Obscur: Expedition 33
Baldur’s Gate 3
The Longest Journey
Dark Souls
Civilization 2 & 4
Alpha Centauri
The Outer Wilds
Fallout 1 & 2
Alien: Isolation
Super Mario Bros. 3
Death Stranding
Doom (1993)
Phasmophobia
Psychonauts
X-Com: UFO Defense
The Witcher 1 & 3
Disco Elysium

Java modded Minecraft.

Age of Empires 2, despite being Microsoft owned, is easily one of the best strategy games of all time and has very clearly stood the test of time. It's over 25 years old and people kept playing it a lot even before the HD remakes. I remember reading that the folks that made the 1st game often had to choose between "actual history or hollywood history" for some details, often going for hollywood because it made for a more fun experience.

I suspect Factorio might stand the test of time as well, and it's clearly something made by someone who really understands the medium. I haven't begun my factory yet.

Planescape: Torment does it for me.

More lines of dialogue than all of Shakespear's works? Sign me up for that kinda RPG, lol.

Though these days some good voice actors can do a lot, looking at BG3 here, at least the voice casting.

Terraria

Lost Odyssey. I haven't played Clair Obscur yet, so I one know how it compares, but for me Lost Odyssey is the pinnacle of turn based RPGs.

I'd argue there isn't one. Not on the scale of LotR. It cannot be overstated how unlikely it was that it happened the way it did.

Super Metroid

Morrowind

Outer Wilds

Inscryption

Expedition 33

The best PC game OAT: Disco Elysium

One Shot
Outer Wilds
Portal