I'm not a huge RPG fan but this game looks amazing. You can create your own hero or villain, customize his appearance and skills. Say if you wanted him to have speed like Flash you can put that superpower on him. Theres also the famous DC cities Gotham, Metropolis, and some others. You can't play as Batman or Superman but they are in the game. It's like you do missions for them and try to earn your spot in the Justice League. They talked about this game a little at E3 for the PS3 and this game sounds promising.
This is the stuff that makes me glad i'm a PS3er. Check out this site it has some clips and reviews of it.