The audio out of the SNES was rather quite good, in reality. Music was essentially wavetable based MIDI, and at 32khz, 16-bit stereo, it could accurately spit out 1-16khz in audible range. This is good enough to cover just about any male over 18 or any female over 25's range of hearing. With the "MIDI" being wavetable based, it was essentially infinitely tunable to the specific game at hand. This is something that we made a step backward with on the PSX, reverting to essentially MIDI with a single sample set that had to be shared between all games. This is pretty much the reason that a lot of us remember SNES music fondly, but struggle to place anything from the PSX when heard.
On the other hand, sound effects on the SNES kind of sucked. This is purely a function of just not having enough space on ROM to store samples of reasonable quality.