I like to keep track of my games that I have completed, with most of the games it is pretty easy. When the credits roll, I consider them beat, there are a few exceptions of course like Nier, Resident Evil 2 etc. What I struggle with are fighting, racing games and 4x games. I enjoy these genres, but I don’t know what is “satisfactory” amount that would make me think that I played these games to completion.
Some examples:
- Guilty Gear Strive (or any fighting games that are not Mortal Kombat, injustice or SF6)
- Civilization 6
- Project Cars
Just to add some even longer time goals to the other replies: you could get all achievements for games that have them. Though some of those, like the ones for Civ 6, are excessive. It could give you ideas or shorter term goals to work towards, then you can decide if you’ve had enough at any point before 100% if things get too BS.
You’re right, achievements are excessive in some games, that’s why I don’t rely on them too much. I like the idea of short term goals though, and if those goals seem “fulfilling” then I can use them as my completion milestones.