Indeed....
Genesis and SNES SSFII are slightly different, but overall, the differences are minor. The minor additions made to the Genesis version don't make up for the better graphics and sound on the SNES.
Size:
-the game is 40 megabit on Genesis but 32 megabit on SNES, so the Genesis version is 1MB larger.
Feature differences:
-The Genesis version has four levels of turbo available, while there are only three on SNES. More turbo is always nice.
-The Genesis version has one additional option in the Options menu, "Normal" or "Expert" Super Mode. In Normal mode, you go through the usual game, with 12 opponents and the bonus stages. In Expert Mode, you fight against all 16 opponents, with no bonus stages. Interesting...
On the graphics/sound side:
-The Genesis version has redrawn graphics. They aren't better than the SNES version's though; the SNES definitely has the upper hand graphically.
-Better, clearer music on SNES than Genesis
-Different sounds when you pause (a little cooler on Genesis)
-Maybe slightly clearer voices on Genesis thanks to the larger cartridge? Not sure, maybe not...
And, of course, on an actual Genesis, with a 6-button controller, the Genesis version has better controls unless you have an arcade stick for your SNES. But this does not apply to Virtual Console. Even without the controller I do think I like Genesis SFII SCE a bit more than SFIIT (more turbo with no codes...
), but for SSFII, it's definitely better on SNES.