In 2009, Dragon Ball made an appearance on the big screen through the live-action Dragonball Evolution film directed by James Wong. After I finished watching all five seasons of the original Dragon Ball anime series, I checked out a copy of the Dragonball Evolution DVD through the King County Library System.
The first major difference between the two is how the story gets in motion. In the anime, Goku is still rather young and living on his own after the death of his grandfather; he has the four-star Dragon Ball that was left to him by his grandfather when he died. At the beginning of the live-action film, it is Goku's 18th birthday, and his grandfather gives him the four-star Dragon Ball as a gift.
Another difference is the reduced number of characters that appear in the live-action film. The most notable omissions are Kuririn, Tenshinhan, and Chaozu. Since the film is set in the last couple of seasons of the Dragon Ball anime, it could be argued that Kuririn and Chaozu didn't need to be there, because they were dead at that point in the anime. As for Tenshinhan, my guess is that the scriptwriter couldn't really find a way to incorporate him into the story they were trying to tell. I wasn't too surprised by the omission of Oolong and Pur-Eh, though.
As for the villains, there was Piccolo and an unnamed human female helping him. The female's name is never actually said in the film; however, if you watch the end credits, you discover that she is Mai. In the original Dragon Ball series, Mai was a henchwoman for Pilaf, not Piccolo.
Personally, I didn't like how Goku was portrayed, and thought that him and Chichi going to the same high school felt rather forced. I also didn't like how in the live-action film, they attempted to combine the early Yamucha (thief and con man who was shy around the ladies) with the later Yamucha (who is too smooth with the ladies).
I also thought Piccolo's motivations were rather unclear in the film. In the anime, he makes it clear that he wants to take over the world and cause terror for the human race. However, in the film, Piccolo first says that he wants to turn the world into a wasteland; this is later followed by him saying that he wants to rule the world. So is Piccolo saying he wants to rule over a wasteland? Also in the film, Piccolo makes it very clear that he despises humans, so why does he have Mai working for him? And it's never made clear why Mai is working for him, because there's nothing to indicate that she'll gain anything personally for helping him.
The origin of the Dragon Balls was also changed for the live-action film. In the anime, the Dragon Balls and Shen Long (the dragon that comes out of the Dragon Balls to grant wishes) were clearly created by Kami. However, in the live-action film, the Dragon Balls were created 2,000 years earlier, when Piccolo was sealed away by the mafuba; the balls were generated by the seven people who cast the curse. Another big difference is how Goku becomes the large ape. In the anime, it happened whenever there was a full moon. In the live-action movie, it happened when a rare eclipse occurred.
One of the worst differences between the two is the use of the kamehameha. In the anime, this is clearly an electric blast generated with ki, and it's a rather powerful weapon. In the live-action film, Roshi keeps referring to airbending with the kamehameha; this makes no sense, since this is an energy blast. Whenever I heard the term airbending, I kept thinking to myself, "I thought I was watching Dragon Ball, not Avatar: The Last Airbender." Also, in the film, the kamehameha is not only used as a weapon, but it can also light torches, and Roshi even uses it to bring Goku back from the brink of death; in other words, it becomes a "deus ex machina." I can buy that it can light torches, since in the anime, we have seen the kamehameha start fires when it's used and blows something up. However, I cannot buy that this energy blast that is used as a weapon can be used to heal someone, especially since Roshi is never shown in the anime as having any kind of healing abilities.
Dragonball Evolution definitely has a lot of problems with it, even if you don't have any familiarity with the original Dragon Ball anime series. I would definitely say that the anime is much, much better than the live-action film.
There's been rumors that a second live-action Dragon Ball film is in the works. While this film did well in Asian countries, it did not fare well in North America. I can only hope that if this rumored sequel does end up being made, that it ends up being a direct-to-video release in North America.