Definitely MKX. I was pretty disappointed at Batman being pushed back a few weeks but if it means it's a better game then it's cool, and it'll also be 2 days before my birthday. I might pick up MLB 15 The Show as well.
I think it'll do really well. Not as well as it did back in the day, obviously, but I think it will sell to a lot of fans old and new. I know it's the game I'm looking forward to most this year since Uncharted 4 got pushed back.