I think most of the obvious ones have been covered.
I'm curious about some that haven't been mentioned, like Hit the Ice, Weapon Lord, Ultimate Mortal Kombat 3, and those two Ninja Turtle games that are similar enough to be considered the same game.

EA's NHL games were always best on Genesis, and it wouldn't surprise me if other EA sports games were too.

Super Street Fighter II for Genesis has more intro and portrait animation than the SNES port, and an expert arcade mode that lets you fight all 16 fighters, but the SNES has much better graphics and sound overall.