maybe 10 hours with brawl trying to unlock everything when it got launch

like 4 hours or so

I beat WindWaker in a single seat back in 2003. It took me from Saturday 10 AM till Sunday morning, allmost a full day.

I also finished Paper Mario GC in a weekend, tough that was not a single session

I also remember that, back in 99, when I was twelve, my mom bought me a GBC with Pokemon Yellow (the Pikachu Special Edition) and I spent all the night playing it, trough Kogas Gym. That was really adictive.
I remember that, when I finally got to bed, with my eyes injected in blood I could still here the damn MIDI inside my head.

About 18 the day I first got my 360. It was great. I went back and forth between Gears, Condemned, and Burnout Revenge.

not straight but I used to play world of warcrack for about 10hrs for about 6 months. I lost alot of my life there hehehe.

Smash Bros. Brawl for 11 hours

24 hrs + 3 hrs the next day playing ffvii
after i stopped, i felt sick as hell.

Probably ~10 hours on Ocarina of Time.

I played Twilight Princes from 12pm to 2am on my final session. So, 14 hours I guess. I also did 8 hours with the first Mario Party. I had blisters from playing all those mini games where you had to spin the analog stick around.

I've played all the Metal Gear Solid games all the way through in one shot. After that I jump right back in for another go until I just have to quit. I would say if you took out bathroom breaks and eating, each of thouse days were around 23:15 hours.