Fantastic art and music along with rock solid level design and good boss fights. Definitely the best game in the franchise that I've played so far.

The game is much more of a refinement of the classic formula than anything revolutionary, though, which was a slight disappointment since I do take some issues with certain aspects of the classic formula. Still, the execution here is hard to critique.

Side note: The passwords not saving what Sigma stage you're on is cruel and unusual.