Minecraft (unlimited things to do)
GTA V (almost unlimited things to do)
Red Dead Redemption II (many things to do)
Ultimately I think I’d end up hating all of them, as I don’t do well with playing games over and over unless they’re online competitive. These three might give me the best chance at longevity.
Sports has a more iconic presentation than resort. But resort feels more fun to play for me personally. I’m curious, why you prefer the original over Resort?
Sports feels less unpolished. You think that would be bad, but the imprecise controls actually make it more “user friendly” and “beginner friendly” aswell. Also boxing and homerun batting are my jam, tennis being a third choice. I line some games on resort, specially the sword fighting and archery, but the rest are to Boring for me. This is all personal opinion though.
I don’t have any posted times sadly, as I only had one run I actually liked (and many, many crummy ones.), and it was not recorded. I stopped running because of personal issues, but Im in the process of moving from where I live and one of my goals is to resume streaming speedruns, specially master system games and randomizers.
Gamecube and NDS original and lite have some interesting GBA options, and Wii has VC and Gamecube backwards compatibility.
But I have to go with:
PC Starcraft 2: Has Broodwar mechanics as UMS maps. No multiplayer hurts, but high skill ceiling and engrossing nature means it shouldn’t get too boring. Include Alphazero AI computer opponents with scalable difficulty, for realistic opponents.
Hollow Knight: With mods, randomizers particularly. Scratches platformer and Metroid style itch. Speedrunable.
Grand Theft Auto: San Andreas: Tonnes to do, and ways to approach this game. I have yet to finish a master save file (everything you could possibly do before the first mission), but that’s been fun as hell in itself. Has good car race mechanics. Has good visual mods too.
noteworthy omissions
Mine-fricken-craft: Redstone contraptions, and artistic outlet could be cool, but perhaps my cell has real-world artistic expression opportunities?
Procedurally generated worlds somewhat prelude stale play.
Morrowind (or some other significant RPG) for multiples different class builds, challenge runs, etc.