It's called evolution because it's not exactly the same as the Tv Series. We see its main character - Goku - studying at school, with troubles with his classmates. That can be offensive for any fan of the TV series, but Dragonball Evolution must be analyzed for its own. And it's a ridiculous movie that could be considered a mix between Shaolin Soccer and Volcano High. But in this movie there's no fun, no good action scenes, and the special effects may have been created by a newbye with Adobe AfterEffects.
Moreover, the story is quite silly. Everything that was interesting in the Tv series has been pulled out, and the new script has added things like an eclipse or an story about a "chosen".
The TV series fans will feel dissapointed and insulted, but any other spectator will walk out of the cinema asking who are those characters disguised like retro-fashion victims... and why that green guy wants to destroy things.