It varies, some days I play 4-5 hours, others none. I used to play much more frequently, but life kinda gets in the way. Now that I have a job (2 actually) and a girlfriend I don't have as much free time available for video games. My last semester of college, I was so busy I played games only about 3 or 4 hours a month, if that.
About 45-60mins a day on weekdays and 1-2 hours on sundays. Never play WoW! used to play 4+ hours daily
I used to spend all day every day playing Diablo II. I won't be doing that again until ladder reset which is any day / week now hehe.
I used to play 12 hours per day for a whole year when i was in middle school. I'm addicted to mmorpg called ragnarok at that time.
I no longer play online games, but somehow... I still get stuck to my computer for at least 4-6 hours per day. I'm just addicted to using computer and the Internet.