Sometimes it just happens. It's a cycle. Something comes along it's fresh. Perhaps more crucially, it's successful. Next minute: every publisher is pushing out their own version of the same game. It can burn you out as a player. What genre are you currently a bit sick of?
I have a couple. Third-person RPGs with the fetch quests. I'm kinda over that. 2D puzzle-platformers with 'retro' aesthetics. I'm a bit over that as well. I'm close to being a bit done with same screen multiplayer experiences -- but man, every time I play a good one I'm hooked all over again.