Embedding is disabled so: 
http://www.youtube.com/watch?v=D7rjLQuW2nQ 
 
I honestly think that no other theme song I have ever heard feels as epic and grand as this. There isn't even a John Williams theme that I think can touch The RoboCop Theme song by Basil Poledouri. I would love for someone to prove me wrong, but I don't think it's even possible.

terminator

Robocop is an epic movie in the first place and has a great theme song but....I am not sure. With Breadfan putting the Cantina Song right there, this is a tough choice.

Terminator rapes the RoboCop theme, and I'm a huge RoboCop theme. 
 
But since someone posted up Orgazmo...it's a VERY tough one to beat. 
 
IS IT THE WAY THAT HE FIGHTS EVERYDAY...OR IS IT THE TITTIES?!

It's been mentioned but I would say Terminator easily. Second would be the intro song from Predator.

What's with html codes auto centering now :S

" Terminator rapes the RoboCop theme, and I'm a huge RoboCop theme.  But since someone posted up Orgazmo...it's a VERY tough one to beat.  IS IT THE WAY THAT HE FIGHTS EVERYDAY...OR IS IT THE TITTIES?! "

Super Metroid was also awesome 
http://www.youtube.com/watch?v=uR7ZqCYNXYQ&feature=related

Some great ones so far, but this is the shit.
 

   
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I love both the Robocop and Terminator themes to bits, but I'd just give the edge to Terminator in terms of being epic.
 
That being said, the Terminator one's been played out so much I'd probably prefer to listen to the Robocop one.

Chariots of Fire.