Just as I'm typing this, I'm recalling other bits I liked about Dragonball Evolution, the fight between Goku and the bullies is a lot of fun, this was probably the best interpretation of Mai until Dragonball Super and the joke with Goku's hair is pretty much lifted whole-cloth from the anime. Where Dragonball Evolution really fails is that the entire production is simply far too lazy. Lazy direction, lazy effects work, lazy adaptation. Sure, there was basically no way this film was ever going to be a direct take on the manga or anime, but it didn't need to be this... bland and generic. A common criticism of Dragonball Evolution is that it "turned Goku into Spider-man", and whilst I can see where that comes from, it's inaccurate; what the film does is take the typical Hollywood template of straight, cis-male, adolescent and give it a handful of DB iconography to wear for the narrative. Sure, that sucks for us fans of the original, but that was all we were ever going to get, and it's not like Fox came around to your house and smashed your DVD collection.
I'll say it again, Dragonball Evolution is bad, but hey, it pretty much was never going to be anything else but bad. Dragonball just doesn't have that much material that really translates well to live action. Sure, I like fan films like The Fall of Man and Light of Hope, but they're still kind of dumb and crummy, just in a fun way. Remember, I read Fletcher Hanks comics and own almost every Gamera film on DVD, something doesn't need to be "good" to be enjoyable. Dragonball is awesome. Silly, illogical, goofy, self-contradictory and fucking awesome. We don't need a serious, high-minded, dramatic take on Goku and friends, because that would suck. It sucks in Dragonball Evolution, not because the film fails to get there, but because the concept doesn't work from the ground-up. Much as I love the Cell Saga or The World's Strongest or the Tien vs Goku fight, I don't need to see them in live action, it wouldn't make my affection for them any more or less relevant. Give this a watch if you haven't, form your own opinion.