I would like to quote a track in a very important part of the game - and spoiler alert, I won't go too much in details for anybody who haven't played (you should, NOW), if you have played the game you probably already figured out what part I'm talking about. This:
And while as I said it's not my genre, I love how a cheerful and happy music, with a triumphant tone, slowly becomes a creepy music when you realize that you have screwed up... and I love the fact that the music is basically the same in those moments, but with little differences that completely changes its tone! And when a music make you feel the precise emotion the developers want you to feel, you know it's a music made right. Seriously, the general story director of Portal 2 is marvelous.