Yeesh...
My opinion? "Eh." It was definitely a worthwhile movie, but you pretty much carbon-copied a generic DBZ plot-line (not that there is a lot to copy in that department); Big, strong bad guy fighting weaker good guys, while each side keeps rambling on about their "immense power" and how "they can't be defeated." ARG! Someone give me a blunt object to shove under my fingernail!
I realize that having to use pre-existing voice tracks makes the plotline a little bit "rigid," but that was inevitable. You could've stepped up the voice-acting (the custom stuff you added yourself) to make it a little bit less groan-worthy.
The good stuff? Great graphics, great sound effects. You've done your homework in those departments, trust me.
All-in-all, try to improve the next one. =P