An explanation: GT was Dragon Ball done right. Mystical, whimsical adventures but with actual stakes, richer characters, better fights, and a better soundtrack, without the overabundance of Toriyama's retarded gags.
Z is the second-best offering due to its incredible fights, very obvious tension--particularly in the Saiyan and Namek arcs, with each villain coming across as a true monstrous and nigh-unstoppable threat--and colorful characters, but the lack of the adventure-style format that makes GT great causes it to suffer. Far too often does it become about JUST the fights, which, while great, get stale after being dragged on throughout the same dismal locales.
DB is third because of what it tried, and mostly failed, to accomplish. Yes, there was a sense of adventure a la Journey to the West, but it tripped over its stupid gags and fairly cookie-cutter characters. There really wasn't any tension because the entire series felt silly, like none of its villains were to be taken seriously. The format did change near the end with the emergence of King Piccolo, but by then it was just too little, too late--because let's face it: King Piccolo is an overrated and rather boring villain.
Heroes is next because, despite its status as a silly fanfiction, that's exactly what it's trying to be--insane, nonsensical fights and situations that are talked about but could never happen anywhere else. It understands its place in the series and fills that niche quite well, but said niche is not for everyone.