I've listened to a few soundtracks from games I've never played. A few hundred, quite close to 1,000. That's typical, though, of people like myself; those that are a little bit not normal when it comes to game music. My latest discovery is the Touhou series and there have been a few albums made covering that music (more than 1,500). Crow's Claw (a Japanese doujin group) is the master of arranging Touhou music, by a long shot.
A few others that I've never played (but with great music):
Lord of Vermilion (Nobuo Uematsu), Etrian Odyssey (Yuzo Koshiro), Cyber Org (Yoshihiro Sato), Death Smiles (Manabu Namiki), DoDonPachi ~A Peaceful Death~ (Manabu Namiki), Romancing SaGa series (Kenji Ito), Wizardry series (mostly Kentaro Haneda), OZ (Michiru Yamane).
And Dracula X. It would be mightily expensive to play the original, as PC Engines are not cheap, nor is the game itself. I did play the SNES remake, but that doesn't count.
Oh, and every Castlevania game released for the Nintendo DS (3 of them, I believe). All badass music.