I never timed myself, but I have spent MANY hours in front of a TV (I run from bright light

) I know for certain that I've played these games for over 15 hours in one sitting w/ minimal down time (grab a coke/bathroom):
Final Fantasy 2 (SNES)
The Legend of Zelda and Zelda 2(NES) My dad beat LOZ before me

NFL 2k (DC) (I played most of a season w/out moving from my chair)
Mega Man 1, 2,3 (NES)
Mortal Kombat 2 (SNES)
Legend of Zelda (SNES)
Max Payne (PC)
Unreal Tournament (PC) (hours and hours)
Quake 3 (more hours and hours)
Age of Empires 2 (PC)
Star Wars: Galactic Battlegrounds (PC)
Street Fighter 2 (SNES)
There are many others, including PS games that I cannot think of now.
The longest I have ever stood and played an arcade game w/ no break was about 8 hours. The local Wal-Mart had gotten Mortal Kombat 2 and someone broke into the machine and rigged it to give credits (not exactly honest, I know). A friend and I went early in the morning and spent the day playing.
Now I get bored after an hour of Eternal Darkness (GC) or Madden 2k3 (PC). I guess I am finally growing out of video games.
Well, when Star Wars: Galaxies comes out, I think my social life will end.....