Lets see here....
I've beaten Super Mario RPG in one sitting, I'd once played Dynasty Warriors 5 four, quite literally, 24 hours straight, Xenoblade Murdered the hell out of my sleep for over a weak. I could keep this list going for ages man.
I honestly can't tell you which has done it most. If you can't tell, I have a problem.
Edit: Well, thinking a bit more, I guess the worse case scenario for me was Xenosaga...
We won't get into details on that one...