I absolutly hate replaying games or play multiplayer games without real progress. It's feels like a sin to me. There are so many great games and so little time, why spend that time on things you are already done? I always see that big backlog of retro games and the massive amount of games coming out almost every day. (same thing for movies / series). But there are exceptions like metroid zero mission + fusion, older 2d mario + mario 64 + sunshine and in recent years dark souls, castlevania lots(I needed that smooth 60 fps after playing it like shit on ps3) and witcher 2 (2. playtrought felt like a diffrent game).
edit: I forgot rayman origins and dkc returns, I played through both without getting 100% because I got easily frustrated and only completed the main story for the sake of completion. after the easier rayman legends which I completed 100% with every time run, I just needed more so I relplayed origins. while playing tropical freeze and getting every gold medal I felt guilty so instead of completing tp I replayed dkc returns.