When I say "quality music," I mean music that is jumpy and catchy, and make the experience of playing in the level all the sweeter, music that I am going to remember and sing in my head for days on end.
Galaxy 2's soundtrack is beautifully made, I won't deny it. But unlike the tunes of old, I'm not going to remember the tune by the end of the day.
It's really a matter of taste at this point. Where people prefer epic, slow, orchestrated songs, I prefer bouncy, lively tunes that simply makes my day brighter.
Sonic kinda ditched the 80s rock themes around Sonic 06 and Secret Rings, save for a few instances such as Sonic Colors's Asteroid Coaster and Terminal Velocity zones. It's returned back to the peppy songs it was known for, and took a crack at worldly themes and orchestras, with some results.