I would say anything more than about three hours (and that is still pushing it) a day would be too much video games (possible exception on the weekends when you have nothing else to do).
[24 hours a day. Minus 8 hours, give or take, for sleep, leaves you with 16 hours. Minus 8 hours, give or take, for school or work, leaves you with 8 hours. Minus 3 hours, give or take, for other things (eating, bathroom, shower, conversing, etc.), leaves you with 3 hours.]