ooh, good topic!
when i was a kid, i spent an awful lot of time playing gauntlet at the arcade-- i'm not sure, but i think that was the first four-player video game ever. . . my friends and i would play that game for hours. . . i also spent a ton of time playing 1943 on the original nintendo. . .
when i got my first PS2, i played Grand Theft Auto 3 for mad hours, and that's probably still my all-time favorite video game. . . as far as the game that i've spent the most time playing it would definitely have to be madden-- if you count the entire series it isn't even close, but even counting single editions as seperate games, it would still have to be madden '03 or '04. . . but just in terms of pure addiction, a game called romance of the three kingdoms II for the original nintendo was right up there-- that's probably the game that i could play the longest in single settings, as i played from early evening to dawn on many occasions. . .
ahh, video game addiction. . . i just haven't had it as much as i've gotten older. . .