Games

The Dwarf Fortress community has been doing this exact thing for years now. IIRC, Boatmurdered was also one of these where the save was being passed between multiple folks.

Terraria. You can choose difficulty of the initial save depending on how familiar the players are, and there are several clear milestones that can serve as transfer point (usually marked by beating specific bosses). In a small world, 20 hours is probably doable? You can maybe find a suitable seed for world generation to be sure.

I was also thinking about Elden Ring - despite the game size, the minimum required amount of bosses to beat the game is surprisingly small, and you can also divide the game into milestones. If it's too short (like, if your players are speedrunner), you can add the DLC on top.

It would be helpful if you mention the games that are already in this list. Also, are all the players trying to speedrun the game or playing blind? Do cutscenes get skipped? Do the other players see what happened in the game before they started playing?

A Girl Who Chants Love At the Bound of This World YU-NO took me 80 real world hours to figure out how to get the true ending (branching story, requires specific item usage at specific points in the story), but depending on the platform and intended audience it is not a game I would recommend for streaming. Although the latest remake censors the nudity, its still sexually explicit, and it contains some content I understand is from a different time and culture but I personally find replusive. Beside that stuff the story was fantastic, though. Plus, as a graphic adventure game, it's probably not ideal.

But, if Graphic Adventure games aren't a problem but sexually explicit ones are, Snatcher on the SEGA CD and Policenauts on the SEGA Saturn are both quite lengthy, and lacking in the explicit department. Although Policenauts has a cool feature where loading a game save gives you a summary screen of everything that has happened up to that point, Snatcher does not.

Metal Gear Solid might be a pretty good one, as I remember the game being quite long, cutscenes included.

The Legend of Zelda Twilight Princess could be a good pick as well.

Danganronpa games can be pretty long as well, and are interesting to people who like solving mysteries.

Shenmue could be a good pick because of its QTE sections, which are pretty fast and easy to lose. And everyone loves to see a streamer lose.

Silent Hill or Yakuza series might offer something more interesting.

XCOM 2 can be incredibly punishing to lose, and the game makes it pretty easy to lose.

Ok what games do you have to start with

Any city builder or colony management game.

You can set goals like have X number of population or tech unlocked.

Oxygen not included, RimWorld, Timberborn, Kenshi, Cities Skylines, Transport Feaver.

Cassette Beasts is a creature collector with a substantial single-player campaign and a permadeath difficulty option.

You could also have permadeath as a house rule, which would let you play singleplayer games with traditional campaigns. For example, you could play Elden Ring or Borderlands 2 and commit to deleting the character upon death.

A weird suggestion: Keep Talking and Nobody Explodes is a co-op puzzle game about defusing a bomb. The player who's streaming will have the bomb but stream only audio, not video, and everyone else will have to use the defusal manual to guide them to safely disarm the bomb. You'll have to advance level by level.

Singleplayer Barotrauma run maybe, not sure about difficulty/proper permadeath, I haven't messed with it much, but it could be interesting

or some challenge run in Noita, which is very unforgiving

Hades. Permadeath not really met technically but meh you’ll get the same effect when y’all have big losses (which there will be plenty of).