Civilization 5. Great classical music!

Sacred 2.Blind guardian-Sacred world's...well with in game concert and epic song slaying bad monsters is fun

Must be Prince of Persia: Warrior Within for me. Because back in the day it made me realize that how important is the music for a video game.

The most memorable for me is music from Heroes 3. This was first PC game that I play and this game has charming melodies.

Nox Archaist soundtrack by Electric Moo
Because Basilisk stew
Tastes better than
Eating a wizard’s shoe!

For a retro Apple II game to have an accompanying fully orchestrated soundtrack is truly ground breaking.
That this soundtrack is also available in a stereo as well as quad/surround mix harkens back to the peak of audio tech from the same time period as the Apple II’s heyday.
Whether playing Nox Archaist on original hardware or via emulator the accompanying soundtrack provides a truly immersive experience pushing the limits of what would have been possible back in the day.
It also makes a great accompaniment to tabletop gaming sessions.

Beware the Isles of Wynmar! Fare thee well…

Going to have to say Mirror's Edge. It's such a fantastic soundtrack that perfectly complements the visuals in the game and vice versa. Says somethng about the tracks when I still play the soundtrack in the background when I'm working. And then there's of course the theme song!

Vanilla World of Warcraft, I still play that album every now and then

I would go with Rainbow Islands 2 Parasol stars because it’s the first video game ever I completed or Colonization which has all those neat midi tunes. ♥

My all time favourite of course is the Morrowind soundtrack but that one is almost too mainstream to tell other people about it… haha

Castlevania Dracula X for the SNES. That bass line in the first level as I whipped skeletons into piles of ash definitely sticks with me.

Not to be obvious, but actually it is HoM&M 3 for me. The music which is present when you are on the game world view is so nostalgic to me, it really invokes memories of sleepless summer nights when my brother and me were so desperately trying to conquer Steadwick... back then (being only 12 years old and with no internet haha! that seemed like such an impossible scenario so we kept trying over and over again... and the absolute elation when we won! Little did we know of what other difficulties await us haha, but it was such a wonderful time.

The specific town music is beautifully composed, you get a sense of flavor for each faction so well. You don't get to see such detail when it comes to music nowadays. The Rampart theme is beyond mood!

And the battle music!!! "combat theme #4" will forever be one of the most awesome tracks for any kind of fight scene. Unreal epicness!

I really loved Populous: The Beginning. It was so ethereal and big and calm. It made playing the game 100x more immersive because you felt like you were on a tribal planet with supernatural powers. Even though it repeated I could listen to it for hours because it was so natural sounding, so relaxing.

I would say I liked the Witcher soundtracks myself. I even bought the movie playing the soundtrack

The heroes of might and magic 2 soundtrack. When I got a PC in the 94, played a lot of games, but none soundtrack catch my atention. The MIDI music was ok. Was here, and did it's work. Until I installed and started the HOMM2. Suddenly, a real orchestra with chorus flodded my speakers. I was shocked, amazed, and every theme was better than the previous. I loved it so much that evel listen the cd in my discman, and even today I have the soundtrack in my phone.

Sorry for my bad english :D

Probably Legend of Zelda: OOT. Other than that, and more in the line of GoG's catalog, I'd say Morrowind. I've played that game for countless hours and I always come back to its OST, best ambience for whenever I need to concentrate. The feeling of wonder and adventure is condensed into every track, in a way that Oblivion's and Skyrim's has not achieved in my opinion.

Quest for Glory V. First time I had a game soundtrack on CD. I was blown away that the dust jacket that came with the soundtrack disc showed photos of the composer and real instrumentalists instead of the bleeps and bloops (Though I also love bleeps and bloops).