Kirby's Adventure, Mega Man 6, and Batman: Return of the Joker are some of my favorite NSFs.
I'd also like to recommend Live-A-Live for SNES, by Yoko Shimomura (composer of games like Legend of Mana, and Kingdom Hearts), and you can't listen to SPCs/RSNs without listening to Treasure Hunter G.
Hit up SNESMusic.org for SPCs/RSNs