This thread actually caused me to sample different versions of SFII through emulation, a game I still have very little interest in. And it's actually kind of funny to me now what little differences are actually there. The stuff is really window dressing when you think about it. Of course, I'm no aficionado of the arcade original, and maybe that's the problem, I don't know, but it seems to me that the essence of the game was captured pretty well in each version. I was actually impressed with what they pulled off on the TG-16 version. Having never played an actual TG, or even known anybody who ever owned one, makes it news to me. That's about all I can add to this argument though.
As for MK, the first one sucked visually on the Genny, but it was pretty playable. The SNES version was visually superior, but was a monster disappointment in how it played. Given that, you have to give the nod to the Genny version. The second one, the SNES version gets the edge. But at the same time, it's not like Genny version was bastardized. It still played pretty well, and I actually liked the music on it more than the SNES one. And yes, the style of graphics that MK used does not hold up as well over time as something like SFII does. The whole digitized thing simply doesn't age well. Part 3 I wouldn't know or care about because by that time I was on the PS1 version.