Right now the only option when it comes to the Avengers Initiative game from Marvel is to play as a giant raging green mass called Hulk. However, that will be changing with the new Episode 2 for Avengers Initiative which brings Captain America into the mix, someone who is a bit more tactful and level headed then Hulk.
Captain America gets some good treatment in this new episode with combat upgrades and even customization of the man himself with different costume choices. While Hulk was charged with just beating the crap out of every villian he stumbles upon in his green filled rage, Captain America has been ordered to find the mole inside S.H.E.I.L.D itself. Giving a bit more of a delicate job to Captain America instead of the Hulk seems like a wise choice.
Speaking of the Hulk, he now has some new outfits as well should you feel like you've seen enough green. For those of you wanting to grab Episode 2, you can do so when it is released by spending either 10,000 ISO-8 (the in-game currency you collect over time) or $0.99 through an in-game purchase for those of you who don't have the patience to collect all of that ISO-8. As of right now the update with Episode 2 hasn't gone live yet but it should be arriving any time now.
For those of you curious as to what heroes will arrive in the next couple of episodes, they will be Thor and Iron Man.