Each playable superhero has their own style of play, which makes it appealing since they have quite a good amount of characters on launch. Sadly, you don't have all of them unlocked when you start off. You are given a choice to pick one hero to start with and from there unlock the rest by simply playing the game. Or, you can spend your hard-earned real cash to buy the hero that you want. Again, this is a Free-To-Play, it kind of makes sense.
When I heard it went live, I left my computer all day just to let it go and download. Thankfully, the client was ready for me to launch the game. currently playing and started with Daredevil. Not the best choice in my opinion, sorry daredevil fans.
Marvel Heroes Launch Trailer