Dragonball is too goofy for the live action treatment. If you try to do a direct adaptation, it's going to be unintentionally funny. If you try and ground the designs, the fan boys that take the series too seriously are gonna be ********. I'd say keep doing Super movies. This doesn't need a live action adaptation.
Same with
One Piece...and pretty much most of Shounen Jump's fantasy action manga/anime titles out there, with the exception of the more grounded story like
Slam Dunk or
RuroKen.
The key of adapting any of Japanese property like this is you have to GET and understand the spirit and the core of the theme as well as the story. You just cannot do it just because of the trend or just because you love watching the anime or the manga, without ever understanding the message or the theme behind the story.
That mentality is what gets us many bad adaptations like Dragon Ball Evolutions, Bleach, and Full Metal Alchemist, etc. (Notice that some of them was made by our very own Japanese production, so I won't say that any adaptation of Japanese manga/anime has to be made by Japanese company whatsoever as that is not a guaranteed to be a successful/good adaptation as few above are already showed).
so, if there is someone out there in Hollywood who happens to GET the theme and the spirit, then by all means...do it! With the proper budget as well!
As long as they don't take too many liberties with it, like making it too "Westerny" like the Saint Seiya (Knights of the Zodiac) live action has shown, as it could potentially lose the spirit and the theme of the story. And usually I don't take any issue with this stuff as much as many in the US, but like I already pointed out, for title like Dragon Ball , given the background behind the creation of this world and its character (Goku in particular), which heavily borrowed and inspired by Eastern Asian sphere, I think you have to include those elements in the story as well as to cast Goku and his family as no other than East Asian.
Anyway, sorry for the long post...that's my take on this. Haha.