To anyone who is wondering about the SNES vs Genesis debate, it is really simple, but I'm about to overly explain things for you.
The music for EWJ was written originally for the Genesis. The Genesis uses an FM Synth for its music, and has a few sound channels for "samples", meaning audio clips, such as voice, or other sound effects that couldn't be created with the different Synthesizer noises (square waves, triangle waves, saw waves, etc.). Because the music was written originally for this set of hardware, a few extra tricks were allowed to make the sound more full. The synthesizer can produce sustains, reverb, and fantastic stereo separation, although the samples could not (they could be switched to left, right, and both channels, but could not smoothly "pan" across like some sounds do).
The SNES did not have an FM Synth in it, and instead relied on a chip that contained "samples". Because of this, developers were very limited in what the audio could do, unless they provided their own samples. The reason the SNES sounded so muddy was due to space constraints on the cartridge. EWJ was a very vibrant and colorful game with a lot of animation and sound effects. Factor in the need to have a sample for each instrument in almost every song (if not every), and your space starts to get smaller. Because of this, the samples were compressed to a very low bitrate, much like an MP3 being compressed further and further. The lower the bitrate of the audio file, the smaller the size, however, the worse it sounds. Also, since these were samples, the SNES couldn't stretch and warp the sounds much like the Genesis could (although it could change the pitch). On top of all of that, only so many sounds could be played at once. The Genesis also had these limitations, but was able to cope much better.
On the plus side for the SNES, however was that many games looking for a more realistic sound had much better success on the SNES due to the fact that "real instruments" could be played. The developers could simply record a single note from any instrument, put it into the code of the game, and then alter the pitch as needed. Because of that, games had a much more "realistic" sound.
Both systems did a great job at the music, but ultimately it comes down to one simple fact: The music is going to sound better when it's playing off the hardware it was designed for. In essence, the SNES music was like a port of the Genesis music, and just like a port of a game to another console, some things get lost in translation. Doesn't mean it's worse, but it's not the exact same.
That was far more explanation than was needed, but I'm sure someone will have enjoyed a small lesson in MIDI music.
