The Genesis may have had the potential to sound amazing, but its complexity limited those unskilled in the art of FM synthesis. The Super Nintendo, however, sounded better on average (in my opinion) due to its simplicity. Instead of working with over forty knobs, trying to get the sound you want, the Super Nintendo's SPC700 accepted samples, which could be altered to achieve different pitches. In a sense, it functioned much like a tracker, which we'll undoubtedly get into some other time.
The SPC700 was, believe it or not, manufactured by Sony. Of course, this was before their advent in the console scene. The sound chip provides eight channels for composers to work with, allowing complex orchestral scores to be produced like those of Uematsu's.
There isn't too much to say about the SPC700, due to its sheer simplicity. Although you might find it interesting that people have created ways to rip the samples from SPC files, allowing for the creation of SNES music through the use of trackers and digital audio workstations. For information on .spc files, which can be used to play back SNES music, check out the post I made a couple of days ago.