This is not the game it could have been. Even with the very simplistic fighting (mash a few buttons repeatedly), it could have been much better. The storyline isn't all that coherent, and as often as not the "missions" don't really make any sense. Add to this the very, very repetitive levels where your main goal for the game is to fight wave after wave of typically-unbalanced enemies.
The game's saving grace--in fact, the only truly good feature--is the ability to fight other human players. The A.I. is so hideously stupid that it's almost laughable. The random enemies are rather unbalancing, as sometimes a character must face hordes and hordes of some type that they aren't all that well-equipped to handle.
As a die-hard Marvel fan, I feel let down. The only reason I'm keeping this game is the ability to fight with Marvel characters against my friends. The single-player mode is just too clunky--with no lock-on ability, a camera that moves around in unpredictable ways, and no ability to detect an attack coming from off-camera, it really feels like the game had potential and didn't just miss it, but missed by a mile.
I never thought I'd say this, but for Marvel fans, I'd have to suggest using a cheat device to access the things normally "earned" through game-play. It makes it a lot easier when you want to battle your friends.
On the whole, it's not the game it could have been.