My gaming habits have me obsess over one genre or theme at a time, and I play that genre/theme to the exclusion of all others. Whether the games are brand new or DOS-era old, I will play through all the games I have of that nature or as many until I get bored, then I usually avoid gaming until a new genre tweaks my fancy.
As an example, I once went FPS-crazy and played Doom, Doom2, Doom3 + Exp, Prey, Pariah, Fear + Extraction Point, Crysis, Far Cry, Return to Castle Wolfenstein, Halo, Halflife 2, Portal, Halflife, and had just begun Blue Shift when I finally grew tired of FPS'ing.