1. Grim Fandango
This is quite literary the game that got me to start listening to video game music. Now this is a game which I love, even though I never got that far in it. I think I never got to the first case. So much fun, and this was me failing. Peter McConnell does such a good job, and I think I never got past Swanky Maximino in game. Listen to the whole thing constantly because of having the soundtrack. I love what Peter says on the song. Since I don't know how do the spoiler just going to give a link instead. I would have to say Peter McConnel is one of my favorites, since I love his work on Psycronauts and hate how underplayed his stuff is in Brutal Legend. Though no matter what work he has done, I keep going back to Grim Fandango as the soundtrack that got me to appreciate music in games. It is so well done, that I keep coming back to it.
http://youtu.be/Pd7oo1biPBE
"This piece is called Swanky Maximino, and It plays in the office of Maximino, the gambling kingpin in Year 2. I wanted to evoke the sounds of speakeasies of the Prohibition Era, those of the smaller "big" bands that played in clubs in such places as Harlem in the heyday of the Thompson gun-toting gangster. Maximino to me is an archetypal gangster character, a man who prides himself on having arrived in the world, and he has spared no expense in decking out his gambling club to show it. The music he would listen to, and the kinds of bands he would hire to play at the club, would reflect that sense of opulence as well. The main part of the music is inspired by recordings of the early Ellington band, when the Duke led the musical part of the Harlem Renaissance in the late twenties. The bridge, or middle section of the tune, is inspired by the aristocratic sound of bands you might hear in the old Thin Man movies of the early thirties. For the most part, we used live musicians for this recording, and I think they did a great job of capturing the style and musical feel of that era. Their use of period-style mutes and plunger effects on the trumpet and trombones is to me particularly authentic, and gives the tune a comic kind of menace, perfect for Maximino's personality."
-Peter McConnell
2. Gunstringer
Another game which most of my experience is threw the soundtrack. I have a large love for Ennio Morricone work, and Gunstringer gives that feel while creating the same feel of Segeroni's movies such as Good The Bad and The Ugly, Duck You Sucker, My name is Nobody, and A Fistfull of Dollars. Most Ennio Morricone worked on. Il Mercenario by Ennio Morricone seems to be a direct tribute to with Bayou-Rollin' Down the River. Red Dead Redemption would come in second place here, because it does a lot of things similar. The only problem was that not all worked outside of the game. Gunstringer on the other hand can listen to day after day with it sounding good. Not the same case with Red Dead Redemption, but that had the same problem as Max Payne. Lots of good atmospheric songs, that created a mood so perfectly in game.
http://youtu.be/4OeQPHCscIE
3. Ilomilo
This is one, that comes from great sound direction. Each sound seems to be a little movement. Much like the music that was in nature. Not only that would always lead to this light hearten move. Each time I hear it in game or outside, it sounds so beautiful nature. I keep thinking of this as little bells and wistles I might hear walking down the street. The drum the footsteps, the taps the things in my pocket shaking. Adding in the kazoo which sounds like little bugs scattering around.
http://youtu.be/2UUpBLviT1k
And to download some of that for free.
http://blog.ilomilo.com/2010/07/ilomilo-loves-music/
4. Sudeki
One I list because I don't think Tom Colvin gets enough love. This is one of the first video game soundtracks I bought. This was back when you could find them in the soundtrack section at a Walmart. Every music, big or small paints a picture of what you will see visually. Take the first town you are roaming about of New Brightwater. Get this warm and happy feeling. A place of home, then you are shown this bright town. This is the cd I have in the car for when I need to wait for someone. I get utterly lost in music. I can't drive simply because I can't pay attention to the road most of the time.
http://youtu.be/gKr_SmUA63E
5. Mass Effect 3
This is the one, you know why. I don't really have to explain. The series as a whole worked well. The first one generic sounding, the second just building to the Suicide Mission. It is played over and over threw out in small parts. So when you hear it, it has just an emotional pull. It is done so well, but it is mostly that one track. Now with the third having so many of these representation pieces. That set the emotion. This is right out the gate with Leaving Earth.
http://youtu.be/iasrOjeOVaI
Still one of the most powerful peices where I get taking back to this emotion every time I hear it. That is just starting out, they have so many moments threw out that you don't notice. Work so well on their own. The Ardat Yakshi Monastery for example.
http://youtu.be/-IIOnY_-tbY
So sublimely done, giving this feeling of dread. It made getting the special edition worth while for the soundtrack alone.
Now this is based off of what I own. Maybe if I took a longer while I might say differently, but this is the list I love and listen to. Enough that I paid for a good lot, and still listen to it.