Excellent movie
I just wanted to say that the flash animation in this is top-notch for a [mostly] solo endeavor. It's certainly nothing to scoff at and while there are some proportional and animation issues here and there, overall I'd say it was still amazing work. Scenes such as the missiles flying in space were on par with a cartoon you'd see on the television. I couldn't really keep track of the plot, although I really didn't care either because... well, it's Sonic. Who really gives a crap.
The only other thing I would have to say is that it's kind of a shame you had to dedicate so much time to this movie! Granted it's one of the top-tier flash animations, I'm not sure the outcome of this would've warranted such a long development time. You clearly have talent that could be put to so much better use than a 4-year-long fanimation...although if it's what you enjoy, then props to you. But maybe next time ask for some help in animating it so you can churn out more work a little quicker!