downright amazing song, but there's a problem, it can't be used in gd

Sounds cool! I think what you were going for was something grand sounding, but the chromaticism in the melody didn't contribute towards that goal. I would advise sticking tightly to a single scale with this cinematic type of stuff. Also, try not to have a low instrument play a melody unless it's a solo. Overall though, sounds well put together and nicely structured with the gigantic crescendos. Cool!

A few side tips: Try to use interesting harmonies! If you listen to John Williams, he does this often (e.g., he uses chromatic mediants in Star Wars). Other types of "out-there" harmonies include: neapolitan chords, secondary dominants, common tone resolution, the list goes on.

Shoehorn some big skips in your melodies! Again, John Williams does this a ton. Just listen to Star Wars or the Superman theme. Adding skips, for whatever reason, makes the melody more memorable. Try it out, seriously!