Which game's soundtrack is best for you? For me Fallout 3, Alone in the Dark's and Age of Conan's sountracks are awesome in 2008. Also for the past game I love Silent Hill series, BioShock, Hitman series and Beyond Good & Evil's soundtracks.

I always liked the tomb raider ones, they seemed to fit the type of game perfectly.

The first Command and Conquer. I even have the music CD of it.
Panzer Dragoon Zwei (sega saturn) had a fairly cool selection of tracks.
Also: Outrun. Mainly the original Arcade editions.
A good dozen or so games from the c64 era. Love those SID chip sounds.
Honestly, I had a good look through the 'newer' games on my shelf, and while the soundtracks are rather good in some, they just aren't that memorable. Nostalgia bleeding through my preferences I guess.
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The best soundtracks are the ones you don't quite notice because of how well they fit into the game. They may not be rocking, hi powered or noticeable, but they help all the other elements work and come together.

Oh the total war games usually have excellent soundtracks as well.
Afterlife had some really lovely music as well and who here has NOT had one version or another of the monkey island tune stuck in their head at some point? They made reference to that themselves, one of the pirates working in the barbery coast said he'd had this tune in his head for days

Sountracks i enjoy are
Command & conquer/Red alert
The witcher
Sacred 2 (nice rock music)
Might & Magic 6 - 9 had some really nice tracks
and spellforce

I've always liked the Guilty Gear soundtracks, it fits the gameplay and is good to listen to while not playing :).
Other than that I also really like the God Hand soundtrack.

To me to the most memorable soundtracks are:
Lemmins (1, Oh-no and Tribes)
One Must Fall 2097
One Must Fall: Battlegrounds
Warhammer 40k: Chaos Gate
Planescape Torment
Tension
Chrono Cross
Persona 3

I like the following soundtracks:
Space Rangers 2
Uplink
King's Bounty
KOTOR (hey, it's Star Wars music ....leave me alone about it hehe)
Divine Divinity
Vampire The Masquerade : Bloodlines
Planescape Torment
Doom 2

C'n'C of course (Frank Klepacki's music is great)
Universe at war (because Frank ... you know what :D )
Prince of Persia: Sands of Time and Warrior Within
Chronicles of Riddick: Escape from Butcher's Bay
Knights of the Temple (shitty game, great soundtrack)
Final Fantasy series (in overral, soundtrack is not so good, but piano versions are sometimes beautiful)
Phobia 3 and Iji soundtracks (nothing special, but I won't forget them)
TES III: Morrowind (main menu theme is so great)
That's pretty much it :D

1. Age of Conan
2. Gears of War 2
3. Silent hill 2

Bioshock: Both the score and soundtrack
Beyond Good and Evil
Fallout 3
World of Goo
KotOR
Final Fantasy VII
Portal: Yes, the credit song is great, but the rest of the music is good as well.

Red alert games.
Total war games.
Chrono Trigger and Final Fantasies 7 to 9
Perfect Dark and Goldeneye.
Audiosurf! But eh...thats my music, so I guess it doesn't count.

1. Outlaws (PC)
2. Deus Ex (PC)
3. Crusader: No Remorse (PC)
4. Zombies Ate My Neighbors (GEN)
5. Ecco the Dolphin (GEN)
6. Wing Commander (PC)
7. Kirby's Adventure (NES)
8. Duke Nukem 3D (PC)
9. Road Rash (GEN)
10. DOOM (PC)

Soundtracks:
-WOLF (the cd version of the game had a very good soundtrack)
-LOOM (it was good enough even on a pc speaker)
- NOCTROPOLIS (it also had a nice sountrack)
EDIT: added noctropolis

Definately the original Alone in the Dark soundtrack (first played AitD when I was about 10, scared the shit outta me.)
Would add to the CnC love-in, I regularly listen to the CnC1+RA1 soundtracks.
FF7 is a fave of mine, got some great remixes.
Absolutely love the Ultima music, especially from U6, U7 and Underworld 1+2.
Elite 1-3 introduced me to some classical tracks
Daggerfall has a great score
Doom is fantastic
Quake II is bloody brilliant
Of course the Monkey Island series is super.
And you can't forget the magic of Sierra games music.
All told, I think I have almost 2gigs of game music... as if I wasn't a big enough geek eh?
Some good sites for you're perusal... [url=http://soundtracks.mixnmojo.com/]Lucasarts [url=http://www.youtube.com/watch?v=4nigRT2KmCE]Something special...