Apart from Mass Effect, Pillars of Eternity, and Deus Ex as others have already mentioned, I’d like to also add:

Grim Dawn.

The conflicts in its Universe feels reasonable, all the factions have their history and reasons of existence, there are beneficial and selfish, but no clear black and white, and everything interacts. The Lore is very good for an ARPG that focuses on combat, loots and built.

Final Fantasy XII is pretty high up there for me.

Bestiary entries are vast, almost a book in game format, and most add to lot of worldbuilding even if not needed for the main plot itself.

Also bosses, sidequests, enviromental cues seldom aren’t at least hinted by a few NPCs often dozens of hours before they’re relevant.

Overall details are often explained when you look in the right corners of the game. Even some weird weather cycles seem to have some logic applied. And in a single case, it felt inspired by a real-world element, one even Mad Max 4 used a cut in the beginning.

And I wonder if the sky-gazing kid in one of the airships that says she saw something in the sky was referring to Deathgaze or the continent from Revenant Wings…

Stalker trilogy, stalker 2

The Portal games, but mostly Portal 2.

Horizon Zero Dawn is to this day the only game I have ever taken the time to listen to/read all the optional little lore drops in the world as I encountered it. Really well done IMO, even if the game is not overall that good, best world building I’ve experienced

Definitely Kenshi. Rather old title where the world feels somewhat desolated, but so well thought out at the same time. Every place has a story behind it

Clair Obscur: Expedition 33 has one of the most interesting world in stories inside and outside of gaming. I hope we will see many more stories set in that world.

The hook alone is great.

So the people started sending out expeditions to find out wtf is going on.

hypnospace outlaw !! it’s more subtle things, of course, since it’s just a sort of parallel reality to our own 1999, but i think that’s what makes it feel SO real. i’m a really big fan of the news page and advice pages you can find in the game because they show you the mundanities of the everyday lives of these people

Ace Combat. Seems rather dull on the face of it but goddamn are the geopolitics compelling.

Suzerain.

I mean, its kind of a given since the game is effectively a politics simulator choose your own adventure romp. But seriously, I don’t think I’ve seen many other games be this detailed. There’s wikipedia page level text for countries, individuals in your and other governments, cities, factions, and others that, while overwhelming, also shows just how many factors and information you have to understand as a president of a nation — it adds to the pressure and sense of responsibility that you have to make heads or tails on all of this.

No matter how good intentioned you are as a president, you’re still just a person. You’re bound to not know everything. You’re bound to be overwhelmed. And your lack of knowledge, intentional or not, leads to bad stuff… Recession, losing your popularity, waning influence in your party, broken family life, assassination, all out war with a neighboring country… Worst of all, you are to blame since they’re all consequences of your actions.

Better get to reading those entries.

I want to answer Xenogears because of all of its story and storytelling, but the worldbuilding itself is kinda standard, if not for the scope of it. You do end up learning about pretty much everything there is to learn - the world and its history, the characters and what moves them, the politics, the conflicts, the geography, the physics, the religions, the supernatural, the origins of mankind - not to mention a full class on philosophy. And then whatever question you still have left, there’s a book about it in addition to the game.

And you start with a classic amnesiac character in a small village.

Trails in the Sky

I got sick about dystopian chaotic worlds that don’t work - where the hero’s journey is about saving the world from some impending ruin, or about preventing a starving dystopian city from being blown up.

In Trails, the conversations you have with NPCs remind you that while you’re on the trail of some bandits or suspicious people, other people are not evacuating, sheltering in fear, etc; they’re living their lives, keeping up to date on modern trends, making travel plans to other countries.

So, so many worlds just don’t have space for characters to have those thoughts. It’s always fear around impending disasters, or how to respond to a fight, or grim poetry about how much the world has fallen into darkness.

It especially hurts that some people live so much of their lives in these fictional worlds that they start to believe people would be like that when they go outside. Worlds like the one in Trails, even if they spend a lot of time being boringly polite, are a nice call back to reality.

Not sure if it’s my absolute favorite, but Pathologic has fascinated me for years.

There are so many strange and unique aspects to the world (especially the Polyhedron, an impossible tower floating above the town) that already make for excellent world building, but when they come together it creates a feeling I haven’t felt from any other world.

You know how Lovecraftian horror has a very distinct feeling? The world of Pathologic makes me feel something vaguely similar, but completely unique - no horror or aliens, but the feeling of powers existing far beyond our understanding combined with people who somehow do understand small parts, and the consequences of their choices affecting everyone… it’s really hard to put into words, but it feels like it created its own genre.

If we’re including fan games for preexisting games, I so far absolutely love Pokemon Empire, the Reborn style difficult fan game set in a region that basically just finished a full-on civil war and you and a friend are finally able to return to the region. Not really spoilers since you are basically told that in the first part of the game.

I am not gonna give away spoilers if possible, but the region feels like it’s divided after the war, which gives it a more real feeling than any official game or basically any fan game. Various NPCs question whether things were better before the war, some want the old monarchy back in power, some are more in favor of the new government, etcetera. It feels less like a typical run through the gyms, defeat evil team, beat elite 4 and champion style game so far with what I have played and how far they are in development.

I like how the writers didn’t just decide to make everyone into a hivemind of “villain team bad!” ( or more than likely just ignore them, like in majority of the official games ) and have people who support them and people who start to question whether or not the villains are in the wrong or not.

I also like how in the tilesets they used, some parts of the region look like they are wartorn to a degree and are a region that is starting the rebuilding process.

I wanna say more things, but then I’d be spoiling stuff and I really don’t wanna spoil things for this game.

Rainworld

…but when you start the game, you are merely trying to survive and explore a living ecology full of hostile creatures. The game doesn’t care if you understand any of the lore, it doesn’t care if you “finish” the game, it’s just there to be experienced.