Shooters. While they can be fun, they get very repetitive after a short while. So can RPGs, but the great part about those is there's so many ways to play them, given that they allow you to, such as Skyrim.
this is gonna sound weird but MMORPGS for me i cant get past the hot bar of skills that just annoys me, it gets so cluttered with useless skills it actually kinda pisses me off but i do like old school runescape and elder scrolls online (let the bashing begin)