Which game do you think has the most epic theme music?

Deus Ex all day long.

I can't believe no one mentioned the Mortal Kombat theme.

Pff, easy peasy, Metroid Prime, without a hint of a doubt:
Listen yo it, and you'll forget that other games HAVE themes

Rayman Legends

http://www.youtube.com/watch?v=qQfGfGLkg6c

Thomas was alone, Crusader kings 2, Painkiller.

Deus ex: Human revolution(icarus theme) and witcher series

Melancholia from Gunpoint

Mass Effect 3

Deus EX OF COURSE

GTA vice city radio is the first thing bump into my mind when i read your article :D

I like Top Gear and Top Gear 2

Far Cry 3: Blood Dragon
I mean, just listen to this!:
https://soundcloud.com/daawatcha-1/blood-dragon-theme?in=baberim/sets/blood-dragon-ost

Fantastic retro track!

Every Megaman series.
But I also found out that a slow sad sounding music is also great for a final boss.

Crysis 2 has great soundtracks.

Mafia The Lost City Haven,Mafia 2,Arcania Gothic 4,Operation Flahspoint Dragon Rising,Brotchers in arms earned in blood.

Super Hexagon

FTL?

FTL?

And not a single mention of Homeworld...
Yep, there are lots of great theme music games posted here, i agree with that, but there is no other game with Homeworld's epicness.

castlevania. Not the new crap, but the old gold

Bastion - Assassins Creed (woodkid) - Frozen Synapse - Braid - Max Payne - VVVVVV - Metal Gear Solid.

Falalan from EU2

There are so many good games and so many soundtracks I love, so I'll just mention the first that cames into my mind: Killer Instinct

Psychonauts

Metroid Prime 3

Anything from LoZ Ocarina of time & Majora's mask, heres one of my favorites

Ratchet & Clank 2 and 3...despite being a more kid-friendly game, the music feels pure EPIC.