Oh yes! Actraiser! Great tune! Another one of those Castlevania-esque tunes.
Here's some specific examples of some tunes I thought were pretty cool.
Bloodrayne: Betrayal - Dusk Falls - by Jake Kaufman:
I love the Castlevania-esque feel to this. I haven't played this game, but I love this tune. The game looks more like a beat-em-up than a Metroidvania, so I don't know if it's something I'd like as much (although I do enjoy an occasional beat-em-up). But this music makes me want to give this game a try.
https://www.youtube.com/watch?v=i0YO617O8lQ
Also, the NES-style of the same tune:
https://www.youtube.com/watch?v=5yBeYJ6L9qY
Shantae: Risky's Revenge - The Labyrinth - by Jake Kaufman:
Mix Metroid and Zelda, then put it in an Arabian Nights theme with a half genie heroine, and you have Shantae. An awesome series of games with equally awesome music. This tune is cool... its like a Zelda dungeon with an Arabian Nights flavor.
https://www.youtube.com/watch?v=KS125kQnyHw
Phantom of the Asteroid - Title - by Rob Hubbard:
Of course I would need to mention Rob Hubbard! He's made a lot of great tunes on the ol' C64. This is just one of many!
https://www.youtube.com/watch?v=rYx92zAF-IE
BreakQuest - Quest - by Thomas Mogensen (aka Drax):
BreakQuest was an Arkanoid-style game that didn't seem to get very much attention, but was an awesome game. The music was all tracker mods, and they were some awesome tunes! Here's one of my favorites from the game.
https://www.youtube.com/watch?v=ORbxMJq7470
Megaman 5 - Protoman Stage:
The Megaman series has a lot of really cool tunes. I thought this one was very cool:
https://www.youtube.com/watch?v=L-shOSPV7q0
Megaman X4 - Opening Stage X (Sky Lagoon):
The Megaman X series also had some good music. I like this one a lot.
https://www.youtube.com/watch?v=ci13Gc6_SDI
