This isn't about what soundtrack is the best, but what soundtrack is the best when combined with its game. And it doesn't have to be an original score.

For a complete soundtrack, my best fit is probably MGS4. It took the game up the last step on the epicness ladder.

For a song though, I have to say Slipknot - Before I Forget in Motorstorm. Whenever I was racing with that song in the back, I got even more high on the gameplay, it almost feels like it added to the gameplay itself, that combination is simply pure awesome.

I have to say all 3 Halo games. As soon as I hear that tune instantly you think of Masterchief. EPIC.

Metroid Prime. Tallon Overworld 1, Magmoor Caverns and the Space Pirate theme are especially fitting to the moment.

Metal Gear Solid 4 : GUNS OF THE PATRIOTS -Especially in Act 3 Ending.....where liquid says - GUUUUUUNS OF THE PATRIOTSSSSS!

Super Mario Galaxy - Just brilliant and wondrous music in every planet!

Final Fantasy 6 - matches the epic & medievel feel perfectly.

I never owned it but i played it to death, i would have to second the vote for the Halo theme.

Honourable mentions to Mario Galaxy and the overworld theme from Metroid Prime.

Oh and the Phendrana Drifts theme from Metroid Prime.

Only the second theme (Transport Access to Phendrana's Edge).

I was going to disagree with you and say the first one, but then i went back and listened to them both and now i'm not so sure;)

The entire soundtrack of Mega Man 9 is a great accomplishment. It takes skill to make catchy tunes with an 8 bit feel.

Portal - Still Alive