To the game's credit it actually has pretty good fighting mechanics, buuut we all know why most people play the game.
I personally thought Nether Realms's Mortal Kombat was better with tag battles and stuff like that. I didn't feel much of a need to do Injustice's version of the challenge tower and felt they should have taken some effort from that to devote more to the multiplayer experience. However the story mode is pretty good (at least its there which is better than what other fighting games have done) and the arcade endings do have some cool stuff in them, if you're willing to devote some time to them.
There are also things in it that only people who are into fighting games will like. Like statistics for your attacks and stuff like that. The fighting has a hint of strategy to it which is cool, but like I said before, I'm more of a fan of the really fast pace 2D fighting games. If your a fighting game fan I'd say give it a shot, same if you're a DC fan. If you're both, then go have fun.