Vivid Noise - Mega Man 9 

The fortress can be a slog on replay but a truly unique theme per stage goes a long way. I don't need 2 fortress sets per game, but 11 left me feeling empty after mostly similar scenery after Wily 1 and the same song played up until the final boss. 9 and 10 are very solid, my complaint with 10 is just that the ost is generally lower energy even to the point of feeling morose. Just an all around great series all things considered, glad they didn't hard stick to the 8bit format tho