I'll cast my two cents: it doesn't look horrible (edit: okay, yes it does), but because we're spoiled by:
Action movies in general
The recycling of Matrix-like effects
The uniqueness and style of the Dragon Ball series
The fact that Goku being a white kid is logically kin to Tom Cruise being the Last Samurai.
...this ain't gonna' work.
As aforementioned, it's not racist to dislike the idea. Simply put, a white guy having this much status amongst Asians is unlikely. The reason why anime characters tend to look American is because they're geared to American viewers.It isn't bad that asians sought a warrior regardless of his attributes, but it is outright hilarious to witness a white kid named "Goku", already unusual as a name amongst the Japanese.
Goku's destiny was slightly predetermined by his ancestry. Not to say that they chose his fate, but to respect the truth that he was born a Saiyan, specifically as a descendant of Bardock, who fell victim to Frieza the badass.
I'm not being nostalgic or "fanboyish" here (not even my style); rather, I'm being realistic. I did like Spiderman 3, but listen: this is Hollywood's biggest fuck-up since Spiderman 3's Eddie Brock, a scrawny loser with insecurity problems who lost his NY job and went insane. The movie does not have to be the carbon copy of the original, but it shouldn't take the elements of the original, roll it into a fat blunt, smoke it, and use the exhaled vapors as the remains of what we call ideas for a movie.