I have honestly admit that, despite the less-than-perfect production side of this piece, the musical side of it is nothing short of genius! There is not a soul in the world who could metal-cover this piece better than this!
My only critique on this, which I do not count against you considering what you have to work with hardware/software-wise, is the production. The guitars come out great, and there's enough distinction between rhythm and lead. "It's your drums, Marty! Something's gotta be done about your drums!" You gave your kick drum real kick, which is what you want for metal, but there is an overwhelming pulse of lows and mids in it, which makes it come out with a muffled punch like someone's hitting you with a boxing glove on.
What you want, when mixing drums (which believe me, I've been producing digital rock for almost a full decade now, and I understand how difficult mixing drums can be) is to give your kick drum a wet punch. You can do this by giving it enough lows and mids to punch you, but give it some hi-mids to "sweeten" it up. A good example of how I believe (granted, that's my personal opinion) kick drums should be mixed is how you hear them in a Nickelback song - that is the perfect wet punch for kick drums. Of course, in metal, most of the time they're mixed mostly with less lows because they want you to hear the pulsing of the drum rather than feel it.
Mixing is, as they say, a variant discussion that differs from person to person. Despite that, though, this is an amazing metal cover of a great piece from a great game! I actually did my own orchestral rendition of this piece myself ("Warrior's Spirit Within").
Great job and keep 'em coming!