By now you've probably heard the utterly insane news about Mortal Kombat vs DC Universe. Games Radar's first thought was "hm that's 10 years after Marvel vs Capcom guys," but immediately after the inner snark died down they started trying to compile a list of who will and won't make the cut. Then they heard Ed Boon say Batman, Superman, Sub-Zero and Scorpion were all on board and that further characters will be decided by popularity and how well the compliment the other franchise.
What's that mean? Well, Boon claims Sub-Zero is roughly equivalent to Batman because they're both the silent-broody-night-ninja type (not sure about Superman and Scorpion though...), so that means the rest of the characters should have some kind of connection. Armed with this information (and a stupidly vast love of comics) Games Radar finalized this list of incredibly likely inclusions.