DBZ started out as a nice idea. DBZ started out entertaining. DBZ started out with a story...an interesting story...hell, what could of potentially turned into a great story. It had a plot, it had characters that had perhaps a shred of depth...well, no, but they did serve a purpose in the long run and ended up sticking around...unfortunately...
So where did it go wrong? It's pretty difficult to make a sequel series off of a series that already had a million episodes, and try to make it even longer. DBZ ended up turning into a bunch of screaming, pointless bickering, energy charging, anf the same three punch kick punch frames repeated for 3 minute intervals an episode.
Now, certain episodes/groups of episodes did serve a purpose after it began to lose all purpose, namely the ones where main villians were arriving or dying...other than that, it was pretty much pointless.
So what should DBZ have been to have made it perhaps a respectable series all the way through? Eh, get rid of about 200 episodes and all the pointless shit...I mean, there's a such thing as "filler", but...DBZ pretty much erased the line.
Don't get me wrong though...I used to be a big DBZ fanboy, and it's undoubtedly one of the most popular, highly-rated animes of all time...not that makes it great or anything. I'm not bashing it either...I'm just pointing crap out.