Naturally the next one would be The Flash vs. Reverse Flash/Gorilla Grodd/Captain Cold.

After that, could we have Superman vs. Lex Luthor?

I know they were in Confrontations, but let's face it, they aren't very good. When doing the 2v2 game, they are mediocre. They are mostly for support. If you want to play the 1v1 variant, though, they are the worst. Their abilities pale in comparison to the other characters. I feel kinda robbed.