On Steam*:
- Increlution (1552.8 hrs)
- Rimworld (943.7 hrs)
- Cookie Clicker (898.3 hrs)
- NGU Idle (524.4 hrs)
- Oxygen Not Included (472.2 hrs)
Not counting idle games, which have an artificially inflated playtime:
- Rimworld (943.7 hrs)
- Oxygen Not Included (472.2 hrs)
- Team Fortress 2** (336.8 hrs)
- Stardew Valley (234 hrs)
- Fallout: New Vegas (90.5 hrs)
*Not counting games on other platforms (minecraft) or games obtained through extralegal means (spacewar!)
**Also most recently played