1. Not long enough. The movie should have been at least twice as long. It failed to spend enough time developing a plot to catch the movie-goers interest. We don't see enough of Piccolo or of his 2000-year old rampage. Hell, we don't even know how he got out or where he got an airship!
2. No character development. There weren't that many characters in the movie. The only character we really get to know is Goku. Bulma, Yamcha, Chi-chi, and even Roshi-- the only reason we have any idea what they are, or are supposed to be, like is because we come into the movie having already been fans of the franchise.
3. Fails to capture the essence of DB. Dragonball was epic, funny, and full of adventure. DBE is merely a facsimile. The film tries to be epic-- save the world (in under an hour and a half)! It's humor is misplaced (awkward teenage drama). In it's attempt to be adventurous, the group of heroes meets, travels, and wins the day... all in the span of two weeks.
4. Fails to capture the essence of the DB characters. Goku is not an unsure, misunderstood, unhappy teenager (that is the exact opposite of Goku!). Bulma is a selfish, boy-crazy, hothead... her movie counterpart is far too altruistic and fails to be angry enough. Chi-chi is doesn't lead a double life, where her mild-mannered self is the tag-along for the high school jock. Yamcha... actually, he's kinda close. You get the general idea.
5. Taking a bunch of characters and the name of a story and giving it an entirely new dynamic with completely different character relationships does not the same story make! Piccolo and Oozaru did not work together. Even if we say that Oozaru is merely a metaphor for the Saiyans, it still fails.
I could literally write for hours about the shortcomings of this movie... but I'll spare you the ongoing ranting of a disgruntled Dragonball fan.
I'll post Grappler Baki for you guys tomorrow in payment for having to deal with this little tirade. Honestly, I would recommend you go see this movie, just so they'll have enough to make a sequel worth seeing. The problem here is not with the franchise, but with those who fail to understand how good Dragonball really is. If you like the movie, fine; however, if not, please write a letter to the makers of the film letting them know that DB deserves more respect than this.