Awesome thread

There are countless soundtracks from NES games that I enjoy listening to, but if I had to name a single song I'd say the title music to Wizards and Warriors II: Ironsword.

Also, I absolutely love the music to Faxanadu. It's probably one of the many reasons I found that game to be very unique and atmospheric.

Other honorable mentions:
Journey to Silius
Ghosts'n'Goblins
Metroid
Zelda I-II
Final Fantasy