Its because Akira Toryima wasn't involved in it. He wanted the series to end with DB, but the JP company wanted to continue with it cause the income they were making from mangas and action figures and so forth.

Akira didn't do anything with GT, thats why its not as good. Where with DB/Z he helped draw, work on a bit better script and supervised the whole damn thing.

~ KAMAHAME---Oh shit it's happening again.... ~