Disco Elysium.

At first, I thought it was nothing more than a parody of Europe. But then I started talking to the corporation rep on the boat about the world you're in and holy shit. It's nuts how they give you all this insane exposition about how the world works, how physics are different, how there are literal swaths of VOID called The Pale that separate the isuldas and is described almost the same as how crossing space in Warhammer works. Like you need special tech and special protective suits to not lose your mind or be erased, and even then you want to limit your time in the pale. There are fantastical creatures that exist (you may even see one depending on how you play), incredible technologies, and even differences in real tech that become fantastical in the way they are different (like how they have something like the internet, but is dependant on using an actual phone to talk to an actual operator).

I am so dismayed at the fact there are like 3 or 4 Disco Elysium spiritual successors in development right now, but NONE OF THEM are actually going to be set in Elysium, because the world of Elysium would be amazing to continue to explore. 😮‍💨

Dune is incredibly unique. Scifi without computers and genetic magic. All politics. The books are outstanding.

Caves of Qud was my first contact with post post-apocalypse. Can't even begin to convey how strange and magical everything feels in that universe.

The Foundation series by Isaac Asimov. Though, I guess what really hooked me was the idea that the future could be predicted, and guided toward an outcome that would benefit people. That, uh, doesn't seem to fit with reality. But it sounds real nice ☹️

LotR - it's really fucking hard to top especially when Tolkien was pioneering the field.

serious answer: Discworld. every storyline starts out completely separate but through the years they wove together into a world rushing headlong into a new age.

shitpost answer: ace attorney. eat your hamburgers, Apollo.

MALAZAN

I'm only on the 5th book but the world building is Tolkien level of detailed. Writer Stephen Erickson is an anthropologist who brought he and his achaelogist friend Ian esselmont dnd world to written reality. Esselmont has books in the series too but not that far along yet.

It makes it difficult to pick up other books afterwards. Major caveat I didn't know what the fuck was happening until the second book. Then it clicked.

Wonderful writer and world building.

Magic: the Gathering.

It churns out a ton of unique settings and ideas for worlds.

The Elder Scrolls is probably the one I've had the most fun theory-crafting about, but I will admit that you have to pick and choose what to care about.

Also the old Wipeout racing games had a remarkable amount of background plot going on that was really pretty fun. The self-awareness to poke fun at Fusion's poorly-received changes as being the in-universe result of megacorp meddling for mass market appeal gave me a good laugh, but you can piece together a surprising amount of the world from random references in team flavour text

One that just popped into my mind... The Culture Series. I really struggled to get into Consider Phlebas and must have restarted it three times before I got it. After I did, it was very difficult to not think about it all the time. I stopped when life got a bit busy so I do need to pick Excession up again, or restart since it'll all be pretty fresh again by now.

I consider lore and worldbuilding to be related but different concepts. Lore is the details of your world, worldbuilding is the way you deliver those details.

My favorite example of worldbuilding is The Dark Crystal, both the film and series. The lore is standard fantasy stuff, but the intricacies of the world are so rich and they unfold so naturally. It felt like a real world, and I felt like very little of what I learned about that world was simply narrated to me. The world was built through tiny details, interactions and observations, throwaway lines of dialogue, and effectively so.

I really loved Magnamund, the world setting for Joe Denver's Lone Wolf adventure books and their later novelizations.

https://www.magnamund.com/legacy

His Dark Materials is worldbuilt very well, I also like ATLA for its worldbuilding, even if it's a bit simplistic at times.

Dark Souls

I've never played any of the games, but the wikis have so much reading material I can stay engaged for hours.

It's a universe populated by unfathomably evil undead beings. They farm humans for their flesh and their souls, and there is no chance humanity will ever free themselves.

It's an incredibly dark setting, but it's hauntingly beautiful. What kind of society would these creatures develop? Architecture, art, religion. Their civilization is an anathema to us but that's why it's so alien and captivating

Right now I'm way down a Brandon Sanderson rabbit hole, so I guess the Cosmere? I'd say Stormlight Archive, but Mistborn is really cool because they're set at the inflection points in the planet's history. The first arc is excellent, and it changes the world. The second arc is set in the future, with mythologies based on the first arc and scientific progress based on secrets uncovered in the first. The changes in the use of magic are really cool. There's a third arc planned to be set in the future from there.

But the Cosmere as a whole shares some core concepts and characters can move across it, and that comes into other standalone works like (3 of 4) secret projects and a bunch of other stuff.

You know, I've always liked the Avatar:TLA's worldbuilding

Call me boring but Randland (The Wheel of Time).