It would need to be a well-liked game with a lot of nostalgia attached to fulfill the usual requirements of video game creepypastas, and it would have to be one that can be easily hacked.
I think Super Mario World would fill both requirements very well. It's associated with the prevalent 90s nostalgia and was many people's first game, and there are plenty of hacked versions out already.
Actually, come to think of it, I mentioned Ben Drowned earlier and considering Jadusable was able to make those videos in the first place he could easily have done it as a Let's Play if he'd wanted to.