Well as a fan of DC and of fighting games I can tell you that first and foremost, your best bet would be to scour the internet for reviews on the game, they'll give you a better bit by bit break down of the game and give you a feel for whether you'll be into it or not.
As of my personal opinion. While I'm not very good at fighting games, I absolutely love this one. It's sort of a comic book dream match up. No, it doesn't have everybody (and trust me, the die hard fans will cry about such and such a character not being in it) but it does have most of the essential DC power houses. The mechanics are actually very simple, so someone like me who's not very good can still get into the game and pull off all the moves with relative ease, yet there is a layer of depth with them that the more hardcore fighting game fan can pull off some really amazing combo's/moves etc., and get really competitive with it. Another plus side to the game is that like the latest MK game there is a ton of things to do other then fight the computer or go online. The basic "battle tower" mode is in this with a bunch of variations to it for something different to do and then there is also S.T.A.R. Labs which is a neat little game mode which offers over 240 missions using all the characters in the roster. Not all the mission have you fighting another character either.. I won't get into all the variations but just as an example there is one mission where your piloting Superman's spaceship that he came to Earth on, through the galaxy trying to dodge and blast meteor's and such so you can make it to earth, like the old defender game..lol.
All in all, it's a great game. It's a DC fan's wet dream, a good fighting game, and has so much extra content packed into it that's it's definitely worth it. Check out some reviews and video's then do your self a favor and pick this one up..
IR0N MANT1S... that's my gamertag, I'm an xbox guy too.. (the "o" in IR0N is a zero and the "I" in MANT1S is the number one)