I think the Morrowind theme should definitely be in the front page list.
I mean just close your eyes and listen… always gives me the shivers
https://www.youtube.com/watch?v=ZWuNf4gxwuM
Super Mario Galaxy 2 - Hightails Falls Galaxy
https://www.youtube.com/watch?v=o4-kb-32F24
Nostalgia hit me hard in the nuts.
The Darkness, brilliant use of metal.
https://www.youtube.com/watch?v=dwKt9NSINYI
And beautiful tunes aswell.
Kirby 64 - Zero Two Battle Music: https://www.youtube.com/watch?v=BwpLSiplyYc
This could be one of the most epic video game songs ever (well in comparison to all the songs that came before it in the game it probably is).
Wow i forgot about that game
Mass Effect - Sovereign’s Theme
Don’t know why…For some reason I liked the soundtrack in the first game much better than the second.
Command and Conquer - Act on Instinct Ah, the memories…
Tiberian Sun - Nod Crush
Baldur’s Gate - Bandit Melee Again, I think the music in the first was better than the second.
Baldur’s Gate II - Main Theme Regardless, I would often linger in the main menu just to listen to this one…
Neverwinter Nights - Main Theme Up there with Morrowind in my opinion.
The Witcher - Main Menu Theme
Planescape: Torment - Theme
Vampire the Masquerade: Bloodlines - Theme
VtM: Bloodlines - Hollywood
Banjo Kazooie - Mumbo’s Mountain - https://www.youtube.com/watch?v=HCyJhpt_U0Q
Ohh the good old days when Rare still worked with Nintendo. So many classic games they made during the years…
don’t forget this epic theme =D
PoP The Two Thrones
https://www.youtube.com/watch?v=O3UgxdnM2_k&feature=related
https://www.youtube.com/watch?v=xg3-K9Q2Dws&feature=related
Tomb Raider Anniversary
https://www.youtube.com/watch?v=8mizshmeXWU&feature=related
Descent is my favorite, though Deus Ex comes in close second.
Just remembered the Yoshi Story Intro: https://www.youtube.com/watch?v=vLgZ_NnKIe8&feature=related
Annoying but catchy and full of nostalgia.
All the music from that game was good now that I think about… adds to list of N64 games he needs to re-buy
The Machinarium OST blew me away.
Mario Party - Warios Battle Cannon - https://www.youtube.com/watch?v=qhes-AH_YRU
All these difficult minigames, that together with THIS stage made me quit this game while farming for the Bowser Stage.
Shadowman https://www.youtube.com/watch?v=OyO3IvhzfLQ <-- one of the best games ever
and the old Unreal was great 
https://www.youtube.com/watch?v=F2K3aypsv74&NR=1
Contract Jack Theme https://www.youtube.com/watch?v=TdUPPsJZYq8&feature=related
Prince of Persia 08 was just beautiful https://www.youtube.com/watch?v=aUNt0XCWmlw&feature=related
Mirrors Edge https://www.youtube.com/watch?v=kv2lAftt3KE <-- it should be more games like this!
Machines the very best of the time https://www.youtube.com/watch?v=6oMiUEjnPmQ&feature=related
https://www.youtube.com/watch?v=43pMunZUjzk <- badass song from Need For Speed 2 when these games were the shit back then.
just awesome minimal electro^^ I know nothing to comparable
but how foolish can i be to forget [COLOR=‘Lime’]JET SET RADIO ;D
https://www.youtube.com/watch?v=5gO1rwxPvh8&feature=related <— they all absolutely special, no other game had such a funky sound
Anything Orange Box, especially Sector Sweep and Vortal Combat.
EDIT: Also, Rocket Jump Waltz and Subject Name Here.