For trailers on newgrounds a short clip of the animation is better than a lengthy worded out explanation of what your'e creating, Perhaps get back at your creation, smooth out a short battle sccene and showcase a clip of that? Either way don't be disheartened by negative scoring and get at er ---- P.S It may be worthwhile starting with a smaller project for your first one, Cheers!

"A new enemy has returned again to take his revenge."
Read that again slowly...

This "animation" is just absolute trash. I mean dear gods, did you use Windows XP Movie Maker to create this?

Also, ya got a nice continuity error. One moment Sonic and Shadow's fusion is black with blue highlights, then it's blue with black highlights...The fuck?