Daggerfall is long as fuck (in universe, the adventure takes at least ten years.) The dungeons are massive serpentine mazes. Multiple guilds and factions, although they don’t feature overarching questlines - lots of radiant quests, but they never really feel boring.

It’s also fairly difficult - especially if you build a character without cheesing it with a guide. You need to be juggling multiple saves to prevent yourself being trapped in a certain death situation, mess up a quest, etc.

There’s a modern remake, Daggerfall Unity, which a lot of people say is a good way to play it nowadays. The original DOS version is quite playable through DOSBox, and there’s lots of little quality of life tools that you can find online.