Being able to play with a 4 player team with your friends was one of the best concepts, especially considering the fact that it was the Marvel Universe. There were about 24-25 playable characters in this game, though I remember the site having like 100s of characters. That was kind of disappointing in some aspects, I actually had thought I could play as a lot more, but it didn't bother me too much, just playing as my favorite characters was all that mattered.
The plot of the story was pretty solid and interesting. So Nick Fury(head of Shield) forms a huge team of superheroes, including: Captain America, Wolverine, Thor, Iron-Man, Daredevil, Spider-Man, Ghost Rider, Deadpool, Elektra, Spider-Woman, Ms. Marvel, The Fantastic Four, Luke Cage, etc. to stop the masters of evil: Dr. Doom, Magneto, Mephisto, Mandarin, etc. and that's pretty much the whole concept to the game.
This is one of the best games I've ever played, It was so interactive and fun to play. The different Marvel characters you could meet and interact with was very fun. There were fun moments, where you could talk to other heroes and they'd give you their back story; giving their origin and how they got their powers.
Now, the best part of this game is when you forge on to each level, you can start unlocking costumes for each hero(that you're playing as). For example, Spider-Man gets his: regular suit, Symbiote , armored , and the Scarlet Spider costume. This game has plenty of things to do, you'll be playing the story mode over and over again, there's just so much to do in this game that you won't want to stop. I recommend this to any fan of Marvel comics or just to anyone who enjoys RPG games and who just want to have fun!