@Dragoon - It's hard to argue with that tune. Solar Man has a rockin' song as well from the newer games. The best song from the original six games, for me, is a tossup between Metal Man and Dive Man. I like the songs that I can hear being done in a heavy metal fashion.
To answer Tasuki's question, the easiet is MM3's Wily forms. If you're no good with Top Spin, give him a few snakes and he's toast. Warm buttery toast. MM10 has a pretty weak Wily fight, but there's actually some technical dodging involved. The best fight is MM9.
Turbo Man is a nightmare without the Noise Crush and his stage is pretty difficult too. It's the only original series game I've not beat. I'd be more willing to beat it if the Gamecube controls for the Anniversary set weren't jacked up.