If I can get really good at one game, I'd want to be good at Starcraft 2. The problem is it's a lot of work just to become a non-shitty player.
Some of the other games I loved playing back in school are GTA, NFS, Forza, Fire Emblem, Castlevania, Counter-Strike 1.5, some MMOs.
EDIT 1: Also I used to play an RPG called Grandia II. The graphic at the time was simply amazing. Beautiful story, great characters, game play was a little weak but just an awesome game to play overall.
EDIT 2: Apparently Grandia 2 just got re-released on steam. Oh boy.