TBH, I've always felt a bit "meh" to some of the choices for this game. So for me to get back my interest, I need one or two new characters who are exciting, not just costumes. Shuma Gorath and Jill??? Meh...give us Iron Fist, Dr. Strange, Green Goblin or someone.
Also, this game lacks so much in modes, it feels half finished to me. For me, who don't like spending time online with lag and jerks all the time, there's really nothing to do with this game offline.
After playing the demo for MK and seeing all the different features that it will have, I feel that MK will be much better than this game and I'll probably prefer playing MK instead of MvC3. The devs for MK seem to at least care a bit about us offline players. Overall, it seems to be more care put into the whole game than MvC3. And I think many fighting gamers will recognise that and "move over" to that game.