Of the three main series, those being Dragon Ball, Z and Super (I'm not counting GT for now, will get to that later) I prefer the original DB from a literary, storytelling standpoint. It's much more of a hero's adventure infused with mythological elements. Rightfully so, since Akira Toriyama based it on a fuggin' long Chinese folktale. Even in the earlier chapters when DB is still a gag manga full of boobies, pee and farts, it's concerned with its naive-yet-noble hero learning and getting stronger as he travels across a strange world. The final arc is the best bookend. Goku, at the height of his triumph, is thrown into the darkest place he's ever been thus far, literally blown out of the sky and left for dead on a desolate island in despair. To get back on his feet he has to face the hardest trials he's ever been through, including drinking poison, training with God for three years and almost losing to both Piccolos. It's a damned good story, and having it rooted in myths and legends makes it all the better.
With Z, Toriyama takes the lens off Journey to the West and bases it on Superman. Goku finds out he wasn't born on Earth but instead came from a destroyed planet once occupied by brutal space brigands. He continues his journey, but along the way slowly embraces his Saiyan heritage to the point where his desire to fight strong guys overrides his reasoning and sensibilities. If we're still talking quality storytelling the series should have ended at Freeza, with Goku actually dying (and staying dead) for his folly but dragging the universe's most evil son of a bitch into the flames to perish with him.
Everything after that, especially the Boo Saga, reeks of studio interference. Every time Toryiama wanted to end the series or take it in a different direction, Toei stepped in and said "No, the numbers said this and our fans want that."
Now Super. I'm not sure I like what Super has done with Son Goku because in this case his duality has been diminished. Now he's pure Saiyan, living for nothing but big fights and putting all his loved ones in danger because of it. If there's still any real hero left it's a hero with Homer Simpson's brain. It's as if Goku has been replaced by the TFS version.
But hey, it's still fun to watch. I'm interested in where it's going, and especially curious how Goku will return everything to normalcy after his fuckups.
As for GT, well, GT is a big mess. It's Toei with a baby they have no idea how to raise so they keep hitting the restart button. "We want to take it back to the adventure/journey of the original. Shit, that's not working, let's make it Z again. Damn, that isn't working either!"