Wears out after a while.
In my opinion, WoW is a better game (should have spent the 30 bucks on getting Burning Crusade instead of buying this game). But anyway, let's talk about some details of this game.
One of the things I like about this game is that you can rob banks, if you play as a villain, and other things that you can relate more to real life than you can with the things you do in WoW. It's also cooler than WoW in the fact that you can have travel powers such as super speed, fly, etc. and don't have to rely on rides that you can only get at certain places. And being able to create superheroes that look and play like your favorite superheroes is also cool, if you're into that sort of thing. What I don't like about this game though, is that there aren't any real items that a RPG should have, like armor pieces and weapons; the only "items" would be these things called enhancements that you add to your abilities to enhance them. And there aren't really any extracurricular things that you can do like fishing, and the many professions in WoW. Oh yeah, almost forgot, the leveling up process is also more tedious than it is in WoW, so it seems like it takes longer (a lot longer in fact).
All in all, this game is pretty fun when you first start playing, but wears out soon after. I bought a 2-month game card so I had 3 months to play (they give you one free month when you first start), but the last 1 and half months have been wasted because I just wasn't interested in it any more.