Lately, the Red Dead Redemption soundtrack strikes me as one of the best ones ever. Nearly every single song from the game comes off as perfectly composed to fit exactly what was going on at the moment. From those faroff Ennio-ish whistles when roaming the countryside by yourself, to those quiet and solemn mariachi trumpets when walking around the sunburnt towns in Mexico, it was all just. Perfect.
http://www.youtube.com/watch?v=EcdAMFldOis
^Right around 1:25 is when the magic begins.
And then of course there's the "Far Away" segment upon entering mexico. Probably the most utterly memorable moments I've ever experienced in a game.
Although it's a generalization to say I love it when a game's music matches the mood of the events, some soundtrack songs stick out as doing it really goddamned good.
http://www.youtube.com/watch?v=3nQSfyYmoHo
^I first played RE5 on my PC with my headphones on. So when that son-of-a-***** executioner with his dozens of majini goons appeared and began chasing me and my friend all around that village square, it all really made me shit bricks. Probably my most favorite theme of the game and really turns the suspense up even more.
http://www.youtube.com/watch?v=8EzU46LHtIg
^Another song in Dragon Age:Origins had the pleasure of listening to with my headphones on. First heard it when I fought Kolgrim, and honestly I felt the music made the fight even more crazy awesome! After wiping a few times and finally killing that bastard, I preserved my save prior to fighting him (since I loved both the fight and the music) But I think it really fit the mood when fighting the Broodmother. It really magnified her complete horribleness and my disgust when watching her puke acid all over my party members.
http://youtu.be/CAZNX60BzYc
^Anyone who's played Oddworld should share my fondness of the Soundtrack. It's one of those games where the Soundtrack feels like a part of the game world itself. Ellen Meijers did an excellent job capturing that oddworld "feel" with every soundtrack, filling them with ambience you'd hear from the world itself. The chirping of Scrabs in the Mudanchee Vaults, and the metallic rumbling noises of the FeeCo. Depot. for such an old game, it's one of the first I remember that took the Soundtrack as such an integral part of gameplay. It even alerted you when you got the attention of a sadistic Slig.
Videogame soundtracks are really important to me, and I consider them to be one of the most important parts of any game. So I really appreciate it when any developer makes the effort to create a wonderful soundtrack to accompany their game.
EDIT: wtf... why do none of these videos work ;[ Removed the embeds and put links instead.