Subjective again.
Also, I fail to understand how DBZ became so popular.
But then again, with many popular stuff I cannot comprehend the huge follower base (Titanic, Harry Potter, Star Wars, Twilight, Naruto, DBZ, etc..)
DBZ for me is pretty simple, it's designed for like 12 year old boys and I can distinctly recall watching it at 12 and going whoa, he's pretty cool, he's so tough and fierce and just a fighter and so on. Goku was legendary in that sense of just being a straightforward cool guy. It wasn't complicated or fascinating exactly, but at least it was honest, primal and clear character, and being surrounded by overly clever Hollywood movies or TV shows made it stand out by comparison. In my case, I think it sort of reflected a lack of knowledge or understanding of the other anime out there at a particular time and place.
Honestly though, even at 12 when all they did was come up with another super villain after Freiza I lost interest. I had pretty much forgotten about it and then at 18 started discovering all the kind of "adult" anime like Vampire Hunter D or Ghost in the Shell or something like that so that when I looked back and saw Naruto, or Bleach, or even One Piece I thought wow, there is no way I could get into those. I suspect it's the same with Star Wars which possibly also reflected something about the time or place as by the time I finally saw it it just wasn't that interesting.
Anyway, that is my interpretation.