Here is a description of how dbz started.

In the year of 1984, a man by the name of Akira Toriyama started a new project. This gentleman had already been sucessful with his previous project, Dr. Slump, which started out as a manga in the weekly Shonen Jump, but soon became an anime on TV. Toriyama knew he could succeed with his new project if he did things right, and pleased the masses with his fantastic wit and humor, expressed through the manga. What started out as a successful manga, grew into a world-wide phenomenon and is now the most popular Japanese series, world-wide. The project that Mr. Toriyama started, was of course, the tale of a little boy, that grew into a powerful man. It is, the story of Son Gokou, known as Dragon Ball.

Dragon Ball later grew into Dragon Ball Z. Dragon Ball Z focussed more on fighting, but had an incredible plot to go along with it. Unlike other anime like Sailor Moon where the plot progresses slowly but surely through a long series of episodes, a la Power Rangers, Dragon Ball and Dragon Ball Z moved at a fast pace with each new episode picking up where the last one left off. And the manga boasted a total of 519 issues, which were later condensed into 42 volumes which are still being published to this day.

Dragon Ball's final spawn was Dragon Ball GT. It was taken on by a studio that had nothing to do with Akira Toriyama, and was drawn by a completely different set of artists. This immediatley turned people off to the series. But people hated the plot even more. It was a return to Dragon Ball's genre with Gokou and his comrades seeking the Dragon Balls, but with a slightly different twist. Later the series changed tracks and went back to the fighting genre of Dragon Ball Z. This picked up a greater audience, but the show was still doomed from the start. The entire Dragon Ball series had 508 episodes