Well, the SNES had higher quality sound, could produce more on screen colors and had a larger color palate. It had mode 7 effects and I believe it had more on screen sprites and other effects that the genesis couldn't produce. There were a ton of reasons why the SNES was "technically superior".
I would also add this:
"By 1994, SEGA had lost substantial ground to Nintendo in America. The two had been fairly close going into 1992, with Nintendo making strong gains against SEGA, thanks in no small part to the fact that every Super NES came with a copy of the acclaimed Super Mario World. According to market data, SEGA had a 55-percent share. But when SEGA started fracturing its audience with add-ons like the SEGA CD and 32X and Nintendo kept on producing triple-A games for its loyal fans, the battle was won. Nintendo pushed ahead of SEGA, which spent all of its 16-bit good will on the ill-fated Saturn. "
http://retro.ign.com/articles/965/965032p1.html
"The Genesis does have some truly beautiful games, but when you're working with a palette of 512 colors, there's only so much you can do. Oh, the SNES? 32,768 colors, and it could display 256 of those onscreen at once--compare that to the Genesis's 62."
http://www.theflatness.com/2008/11/snes-vs-genesis-eternal-struggle.html
Also, this picture is lawlz