I'm listening to the soundtrack while playing the first game for the first time in ages, and I'm not sure any game has matched it in terms of the overall feel and quality of its music. There are plenty of games with some amazing soundtracks too (Metroid, Zelda, FF, Sonic, Castlevania, Streets of Rage, etc) but I don't think you can convince me anymore that they have better soundtracks.
Just listen to these...I mean just fucking listen:
[youtube]http://www.youtube.com/watch?v=WdZ3821-k8Y[/youtube]
[youtube]http://www.youtube.com/watch?v=B4QHpEn_zRM[/youtube]