Yah, sometimes you stop playing a game not out of dislike of it but simply because while you had fun you also had your fill, doesn't happen too often because generally if I'm enjoying a game I want to see it finished, but there's definitely a few out there that I dropped while still considering a good game.
Witcher 3 is the one that jumps to mind, felt like I got more than enough out of its open world loop by the time I hit Skellige, when one of the missions was like a footrace up a hill or something I felt "yep, I think that'll do me".
While I'm sure I'll finish, it (heck I might do it tihs weekend), Sackboy a Big Adventure is a really solid 3D platformer with some nice varied level design, but I've really stalled out right near the finishing line despite otherwise enjoying it.