Platforming. nostalgia contributes a bit, but remember that some of the most memorable games are platformers.
is it just me, or people are mixing up shooters (gradius, ikaruga, un squadron...) with FPS's (css, halo, etc etc etc)? maybe I'm an idiot, but aren't shooters and fps's considered different things?
anyway shooters (gradius, ikaruga, super r-type) are a close second, followed by rpg's. i used to like fps's a lot more, but it seems that everyone found out they're a gold mine and i just can't be bothered to play all fps's that came out.