Remember when when Mortal Kombat was kool? I loved the game right around the Trilogy era, just before it got all cocky and went all 3D. I loved that game, so much better that the Street Fighter games (which themselves are uber-funky).
That said, with all those X-Men vs. Street Fighter and Mortal Kombat vs. DC Universe games I think we're about due for a Mortal Kombat vs. Street Fighter game. If for no other reason than to see Ryu's head ripped off by Sub-Zero.