Castle Crashers,Risk of Rain 2,Katana Zero,Madness Project Nexus,Henry Stickmin Collection and Doom Eternal.
Changes from time to time. Overall the best game I’ve ever played would probably be DayZ but the game I’ve put the highest amount of hours into would be either Runescape or GTA San Andreas Multiplayer (SA-MP)
Borderlands, specifically the original release on xbox360 with all 4 DLCs. Off and on I’ve probably spent over 1000 hours on it over the past decade.
Pokémon Colosseum and Majora’s Mask.
Amnesia: The Dark Decent, Cyberpunk 2077, Deus Ex: Human Revolution, Factorio, Dark Souls 1
I’m split between RimWorld and Dwarf Fortress. They are so close, and between the two of them lies the perfect game (for me). DF does a little more in some areas than RimWorld, and RimWorld does a little more in other areas than DF.
Like RimWorld is more moddable, but Dwarf Fortress has an actually 3D world and better terrain generation and background simulation.
Portal 2
Stardew Valley