WHERE IS MONKEY ISLAND?!?!?!?!
OR GRIM FANDANGO?!?!?!?!?!?!
PSYCHONAUTS.
All of the Myst games have really great, eerie soundtracks. Awesome stuff.
I always enjoyed Sonic CD's soundtrack (most Sonic the Hedgehog music is decent).
Quest for Glory V (not the best game,but definitely some of the best music)
Beyond Good and Evil is legendary for its amazingness.
Bioshock has a soundtrack on par with movie soundtracks.
Torin's Passage has some great music (a lost gem of SIERRA).

Heroes of Might and Magic 2-4 (2>3>4)
LOTR: Battle for Middle-Earth series (almost the same music)
WH40k: Chaos Gate
C&C:RA series

Oblivion's soundtrack was excellent, but nowhere near Morrowind's imo. Loved it so much, I copied it into Oblivion's music folders.

What are you saying mate? Oblivion's soudtrack is totally diferent then that from Fallout 3. Only a deaf person could say they sound alike.
It's a matter of opinion. It's been a long time since I ever played Oblivion but I still have two copies of that soundtrack at home and in the car and listen to it regularly. It's definitely on my TOP list.

The 'roaming the world' tracks in F3 feel very similar to those in Oblivion. That was my point. But yes, the soundtrack as a whole is different. And i don't disagree with you on the quality. Just wish they had done something different with those tracks on F3.

As far as video game soundtracks are concerned It doesn't get any better than the Silent Hill Series. I have the soundtracks for the first 4 games on my computer and end up listening to them quite often.
Honorable mentions go to Deus Ex, the Hong Kong track gets stuck in my head constantly. Also I must say that Oblivion's music is really well done and just a joy to listen to.

Hitman Blood Money has 2 really excellent pieces, the version of Ave Maria used as the theme song has a lonely sadness that really fits the game and the version of Tosca during the opera level is just superb, best version I've heard and I'm a bit annoyed that I can't find out what performance it was from.

I think the entire Myst series has always had a really great soundtrack, in particular Myst III: Exile.

Jazz Jackrabbit 2 had the most kickass mix. I think they had some dj do it or something, there's a tag like jazzy jeff or something that he says at the beginning of the song. It always gets me amped, its just so cooool. And it was absolutely PERFECT with the gameplay. Words cannot describe.

Demigod has nice soundtrack too.

Came with collector's edition?

Yeap, but I don't have Collectors Edition. :(
I am visiting Youtube to listen the musics. :) I must look iTunes Store, I hope I will find the complete soundtrack on there.

The whole C&C series has a great soundtrack. Doom is pretty good too.

Nothing can beat the soundtracks of Ar Tonelico and Ar Tonelico 2.
In my opinion of course :)

Trine has absolutely great soundtrack.