As I mentioned above, it's clear that
Marvel Super Hero Squad is an attempt to bring the multiplayer co-op style of Marvel's other big game series,
Ultimate Alliance, to a younger audience. In this game's Adventure Mode (the story), two players can plow through innumerable numbers of Lethal Legion minions as you try to stop Dr. Doom from piecing together the Fractal Shards that he wants to combine into the Infinity Sword. With this sword, Dr. Doom will have the ability to bend reality itself. From what I understand, this is the basic plot of the series as well, and while I haven't had a chance to see the cartoon yet, it sounds like it follows the same general direction of the show.
After the game's Prologue level where the Super Squad stops Modok from using the Fractal Shard in a doomsday cannon, the game splits up into six different levels that can be played in any order. Each level features one of the six main characters in the game, and the players can choose a second character to join them (to be played by either another human, the computer, or switched to on the fly if there is only one player). These six chapters have the characters going after a specific shard fragment and while running through each chapter once will get you through the game's story, there is the added bonus of trying to complete the level with each of the support characters provided for that level in an attempt to add replayability. Unfortunately, there really isn't any desire or reward for going back and playing through the levels a second time with the other characters, except for those people who simply can't leave a job finished 100%, and because of that, the game's main story mode feels really short.
Besides the one or two-player Adventure Mode, you can also pit four characters against each other in an arena battle in Battle Mode. Here, you take the four unlocked characters into one of three types of fights. In Time Battle, each member just tries to get the most number of kills in the allotted time, while Score Battle sees which player can get a certain number of kills first. Elimination Battle has everyone starting off with the same number of lives, and the winner is the last one standing once those lives are extinguished. It's in this mode where some of the game's fun factor really shines, but to truly enjoy it, you need to have as many characters unlocked as possible and as many people playing next to you as you can get.