I play to enjoy myself, if my interest takes me elsewhere, it's usually because I find that new game more enjoyable or interesting at that moment in time. I don't feel bad about leaving games behind, or in my 'backlog', I just play what takes my fancy, when I fancy.
I think a lot of folks over think the idea of a 'backlog' and burden themselves with the idea that they need to play all these unfinished games. It's okay to not finish a game. It's okay to play a game for 30 minutes, experience the core gameplay loop and say, I enjoyed that but I don't feel like playing more of it right now.
For me, I often play a game for 30 minutes, an hour or whatever and then I feel like 'I get it'. I understand core gameplay loop and what the game has to offer, and it I had decent time with it, but I don't want to play more, at least not at that moment in time. To use an analogy, I play games like a wine taster, sometimes you don't need to consume the entire thing, to get the full experience. I find this especially true for games that built with clear loops in mind, once you've gotten a decent experience of the core gameplay loop, you're only missing some minor variation here and there. Sometimes I enjoy the moment to moment feel of the game enough to keep playing or even beat the game, but I never push forward just for the sake of progressing, or the idea of beating the game.