Well just concentrate on very detailed playing fields, make the lighting and color correction better than MK vs DC, add more blood, have different color blood, blood stay on the floor, nice meat chunks, use normal mapping, use shadders, and oh ya have cool fatalities.

Instant hit if you do the above, MK vs DC is a good foundation you could just mod that very easily to a awesome MK game.

Again make very detailed backgrounds that don't suck, since you went 3D this has been the worst part of your series.