Well...
The only thing you need is put more effort...
It's good? No.
It's bad? No.
The action is going too fast, like when the Hunter is chasing Master Chief, you could do it more epic, instead of just making MC jump. I know that's because of the limit that the sprites make you have.
You could ask someone make some custom sprites for you.
And another important thing. Size. You don't need to make everyone that big. I don't know about the others but I, personally, like to see the background a little more.
And other about the background. Reach is in hell right now. So to give that idea put some Banshees and Pelicans fighting in the background, and of course explosions.
Good luck!