Well, a “bad” game is subjective, but here’s a few from games generally considered mediocre:
Fester’s Quest (NES)
Clayfighter (SNES) (not the whole soundtrack, but the vocal theme played on the title screen blew me away back in the day.)
Spider Man & the X-Men in Arcade’s Revenge (SNES)
Battle Arena Toshinden
Battle Arena Toshinden 2 (these last 2 were fun at the time but aged horribly, however the soundtracks are exceptional. Sofia’s Stage Theme 1 from BAT2 is among my top music tracks from any game ever.)