Pros: Many heroes and teams to choose from, good multiplayer
Cons: Only one save per device
The bottom line: A fun game, especially for Marvel Comics fans.
If you're a fan of Marvel Comics, your favorite character is probably somewhere in this game, either as a playable hero or an enemy to defeat.

Having not completed the game, I can only comment on what's available during the first few levels of the game.

There are many characters you can play immediately, and a few more you can unlock. Certain combinations of heroes give special team bonuses, which might be helpful during come missions. The mission maps are large, but not confusing, and the enemies offer a reasonable level of challenge. The "pick up and play" feature makes it easy for friends to join your game.

There are a couple of negatives. It's a little odd to continually upgrade established, but that's inherent in the RPG aspects of the game. Health and endurance power-ups can't be stored, instead they take affect when they're released, even if your characters don't need them yet (this can make boss battles more difficult.)

The one feature that's inexcusable is that you can have only one save per device. In other words, no matter how much free space you have on your Xbox hard drive, you can only save one game. If you want to save two, you have to have a memory card. If you want to save three, you have to have two memory cards, and so on. There doesn't seem to be any good reason for this.

Overall, I would recommend this game. Even if you don't choose to buy, it would make a good rental.