Treasure are such a famous developer within the retro subculture that it's hard to call any of their stuff "obscure" at this point, but I want to give my nod to Light Crusader for the Mega Drive (Genesis).

Light Crusader Full Soundtrack on Youtube.

It's got a bit of that isometric controls jank, but it's just got the perfect vibes for a Genesis game. The right level of difficulty (hard but beatable), awesome art, quirky as hell, and one of my favorite soundtracks of the entire 16-bit era. Do yourself a favor and check it out--at the very least, give the soundtrack a listen, as it's some of the best that the Genesis has to offer, in my opinion.