Depends. If exams are coming up(which they're doing so ever more frequently now...) then I'll cut it down to zero but when I'm homework free its usually restricted to three/four hours on weekends and one/onehalf on the weekdays (when there's school)
I spend many hours at the pc generally.. I know than I souldn't but I am.. I going outside with my friends or borther almost every day too. But I spend almost all the rest of the day at pc.
I average an hour, probably. I only play Pokemon and my older games (just got a SNES, and I'm bustin out my N64) when I'm alone, but at friends' houses I usually get closer to five or six hours. Ten, If Smash Bros. or Rock Band comes out.