Technically, I vote on Shining Force 3, Nights, Lunar EB, PDS, PDZ and Astal. Those games made astounding usage of the Saturn sound system, the winner being SF3. There are, like, 6 or 7 voice sample files, and the game bends, blends and re-pitches those few samples to reach nearly CDDA quality.
Nights also get an impressive quality, mostly when plugged into a decent stereo system with good equalization. There are so many tracks in those tunes you need to listen to them several times to identify each one.