Someone mentioned the Genesis version of this game but you're more likely to have access to an XBox. This is one of the few games that is all about cooperation. Two players share health, lives, powerups, and even the screen when they're close together (it shifts to split-screen when you move apart so you can each wander off on your own). It's pretty easy to help out the other player, plus, if you have XBox Live, you could download souped up versions of the characters to make it easier for someone. My ex loved the game and she played almost nothing. Surprisingly, she didn't have much trouble with the controls either.

I really, really wish more companies would produce stuff like this. Co-op and especially co-op network gameplay really needs to happen in a big way.