I still cannot get enough 2-D, low-res, exploration, side-view type games. I love just hopping around and exploring the world.
Examples are cave story, lyle in cube sector, knytt, nubs' adventure.
Of course, the first ones hold a special charm, but each one I play is a little different and adds something unique. I don't seem to tire of it as quickly as other genres.
I also like fast-paced, puzzle action games and slower-paced "Incredible Machine" type games.