The Best Music in Games

NieR - Cold Steel Coffin! This song is so epic win!!!!
https://www.youtube.com/watch?v=WtiJlNmq1PY&feature=channel_video_title

All of The Elder Scrolls in Special Oblivion

Deus Ex definitely!

Deus Ex OST!

http://login.ign.com/prime/promos/bastion/
Bastion OST for Free

Not sure if some people here are talking about DXHR or the original DX. I am really enjoying the DXHR soundtrack. I tend to leave games running for 4-12 hours and play while doing other things (play for a few minutes, pause for a few hours, etc) and I leave the sound on when I'm running DXHR, because the menu music is so beautiful ... now THAT's a first.

teh best vidya gaem ost is cowadoody modern wrafre twwwwooooo

music from Borderlands is awesome.
Borderlands - Mad Moxxi theme!

C&C: Tiberian Sun, Unreal Tournament, Heroes of Might & Magic 2, Amnesia: The Dark Descent, Resident Evil 3

Only considering games where the whole OST is very good. There are a few more games where e.g. the main theme is good but the rest not (like Elders Scroll). So here we go. All the games with excellent OSTs in alphabetic order:
Baldurs Gate 2 (PC), Baten Kaitos (Gamecube), Bionic Commando Rearmed (PC), Golden Sun (GBA), Halo (Xbox), Mega Man X (SNES), Metal Gear Solid (PS1/2/3), Metroid Prime Triology (Gamecube/Wii), No more Heroes (Wii), Sonic Adventure 2 Battle (Gamecube), Sonic and the secret Rings (Wii), Soul Calibur 2 (Gamecube), Terranigma (SNES), UT99/UT2k4/UT3 (PC), WipEout HD Fury (PS3), Witcher 2 (PC)

Secret of Mana :-)

http://www.youtube.com/watch?v=sC0cvwnG0Ik

But seriously though Space Station Silicon Valley had some great tunes you fat motherfuckers I hate you all

duke nukem 2011 the intro song

This thread would be so much better with links in the replies. These are some that I enjoy. Don't expect everyone to like them

Bastion

Bastion

Guild Wars 2

Morrowind

Portal 2 - The National

Portal 2 Ending spoliers

Portal 2 Ending spoilers

From a Gears of War trailer

Dawn of War 2

Dawn of War 2

Dawn of War 2

Dawn of War 2

Command and Conquer - Hell March

I find the Deus Ex Theme catchy. Phoenix Wright's music is quite nice. Two I left out in my original post.

Whale Trail.

Trackmania 2 Canyon

Frozen Synapse
http://www.youtube.com/watch?v=-7vr2I7ipsY

Half Life 2's music makes up the environment somewhat to me. Another to mention.

Just as a little addition, I love all of the music from The Binding of Isaac. Unfortunately though, my favorite music from it isn't heard often unless you purposefully listen to it. The music I'm talking about is the song you hear while you're in the store.
And of course a close second is the music from the final boss fight.