Unreal Tournament had a fantastic soundtrack, still listen to it to this day.
I started gaming way back in the Commodore 64 and i'm all that I time I have probably played 1000's of games but I can not remember one sound track at all. But then I don't listen to music.
I turn off music in games too. But the music on 'The Last Ninja' on the C64 was excellent.
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Silent Hill series (easily)
NFS II & NFS III
Journey
Shadow of the Colossus
MGS 3
Limbo
The Last of Us
Edit: Actually, I'm surprised no one mentioned SH;p
Blast from the past, anyone? The most memorable part hits at around 45 seconds.