When I was in college my roommate would fall asleep playing games all the time. One day I woke up, and he was slumped over in his computer chair with Icewind Dale 2 music playing softly.
Another time I walked in and he was reclining in his bed, eyes closed, PS2 controller still in his hand while the character in GTA: Vice City just stood on a street corner watching the traffic go by. I pried the controller out of his hand and he never even woke up.
I've never fallen asleep while playing a video game. I'm too mentally involved in what's happening on screen, and if I start getting too tired I usually just quit and go to bed.
Maybe I'm missing a truly transcendent experience?