League of Legends probably if we talk about video games.
Gaming
I would probably say morrowind with all the community mods and modern engine.
The fact that there is an open source engine clone for Morrowind is amazing. And there is even Android port for it.
And apparently, there also has been a progress on running Skyrim and other modern BGS games on OpenMW. Mindblowing. Open source community is amazing!
Assassin's Creed Valhalla. That game just never gets old for me. As an archaeologist I think this is as close to being in that time (albeit with it's anachronisms) as I will get.
Is multiplayer allowed? If so, probably Dota 2. For single player, Factorio.
Stardew or Skyrim since I can mod it for more content :D
Pull up a chair and let me tell you about a little game called Nethack.
I've stopped playing it for years but if there is only 1 game I can play, it will be Dota2. In fact I stopped playing it because it took all of my time from other games
Toss up between Diablo 2 lod and path of exile. Just an endless gameplay loop thats extremely satisfying to me
Street Fighter 6. Hell, i know some who will only play that for a few years. FGC be damned.
Edit: Whoops, misread and thought it was for a year. I change my answer to Unity, lol.
Honestly, I already rotate through maybe 4-5 games. Skyrim or Minecraft could probably hold me over.
Single player - F-Zero GX. The skill cap in this game is astronomical - mastering it akin to mastering a musical instrument. There's nothing else quite like it.
Multiplayer - Smash Ultimate. The amount of unique character matchups and interactions is so massive that there's always something new to see.
Considering how many hours I’ve lost to FFXIV, I think that’s gonna be my choice!
Could probably be happy with Hades
Although if Halo MCC count as one game...
Doom/Doom II. Already been playing it for 3/4 of my life, and the modding community still keeps it fresh so even if the core game gets old, there's still things to do with it.