This is pretty good. It could use a little more "oomph".
Also, I feel like you might have played it a bit too "safe" with the musical composition.
As one who personally wants to try and make a Giratina Remix in the future (whenever I can and get enough of the resources to be able to do so), I think those examples could serve as some really good inspiration! There are a lot of interesting parts to Giratina's original battle theme, so I can understand why people may not mess with the musical composition in their remixes, but it doesn't hurt to try and be a bit bolder with it. That's what I feel, anyway.
Hope these thoughts are helpful to you. :)
As I said, this isn't bad work, it just could be much more than it is now.