I think the issue with a lot of Genesis music, which causes people to think it sounds bad, is that the 16-bit era saw a transition to using lots of composers who weren't necessarily adept in the sound programming department. Of course that was a thing before the 16-bit era, but I suspect that as systems began to support more channels of audio, and MIDI became standard/ popular, a lot of game developers would hire someone to write the music and then hand it off to a sound programmer. Or to use tools that made it easier for the composer to 'not worry about it'.
So without proper TLC (just mapping voices to simple FM sounds without much experimentation and care in the sound design), that can get you some very bland and boring soundtracks.
The Genesis can sound great though. I definitely prefer the best stuff on the Genesis to the sound of the SNES.
Ys III: Wanderers from Ys is one of my favorite Genesis soundtracks. It's my favorite version of that particular soundtrack as well. I think it's much better overall than the SNES soundtrack, and the chiptune synth sounds are more likeable than the full redbook audio.
https://www.youtube.com/watch?v=0CvTvcAYtS0
https://www.youtube.com/watch?v=RHoFLQr__WQ
Ecco: The Tides of Time is another one of my favorites. Both Ecco soundtracks are great, providing some very atmospheric and mellow tracks. It sounds heavily inspired by European electronic music (like Bernard Fevre), which would make sense given who made it.
https://www.youtube.com/watch?v=WUvOE1xil7g
https://www.youtube.com/watch?v=32S2oJuANxo
Jewel Master. Not much to say about this one, but it has some ripping tracks.
https://www.youtube.com/watch?v=2ZCghKRIAa0
Darxide is a 32x game, but it uses the stock audio (maybe uses additional 32x audio for SFX?), so it fits in with Genesis/ MD soundtracks. It has some awesome stuff-
https://youtu.be/JwkvjIUD2sU
https://www.youtube.com/watch?v=d8pAVqUoTWI
Streets of Rage 3 has some really impressive stuff too. The first two games have a lot of great sounding tracks and memorable themes (so people understandably, usually like them more). But SoR 3 went off the deep end with trance/ jungle inspired themes and stands apart from the crowd:
https://www.youtube.com/watch?v=Bo2zGky1Jhw
https://www.youtube.com/watch?v=4qRr0KpJRX4