269 according to Steam's count, but a lot of those aren't exactly "games" since it counts everything that's not a movie or whatever as a game. I've got prototypes of games from Mojam bundles, 2 copies of Arkham City (due to the switch from GFWL to Steam), some betas, mods it considers as whole games, and even the old PC Gamer "game" where you could read stuff every month once upon a time.
I got a little crazy when the Star Wars franchise went on sale, everything else I've either picked up during a sale or impulse bought at the height of it's popularity.