For the longest time, the original creator of Dragon Ball, Akira Toriyama, had not touched the franchise since the conclusion of Dragon Ball Z (he was not involved at all in the making of Dragon Ball GT, hence why it isn't canon). That all changed when he created Dragon Ball Z: Battle of the Gods which, incidentally, led to the Super spinoff. And it all may not have even happened if not for Dragonball Evolution.
"Dragon Ball once became a thing of the past to me, but after that, I got angry about the live-action movie, re-wrote an entire movie script," he said in the 30th Anniversary Dragon Ball Super History Book, per Comic Book. If Dragonball Evolution hadn't completely ignored everything the original series was about, Toriyama may have never returned to the franchise. This is ironic because, in many ways, his own Dragon Ball Z ignored everything the original was about.
10 It Got Further Away From Dragon Ball Adventures
For the most part, the original core concept of Dragon Ball was about a group of friends traveling the world searching for the Dragon Balls. The series started to take a shift into more of a fighting series than an adventure about collecting artifacts the closer it got to the King Piccolo Saga, but Dragon Ball Z immediately detoured from the concept with Dragon Ball Z.
DBZ focused more on Goku challenging and trying to beat the Big Bad of each Saga, while the Dragon Balls were just used as a convenient "get out of jail free card" for dead characters. Often, the Balls would be collected offscreen, completely nixing the adventure out of the franchise.
9 Goku Got Dumber
"Dumber" might be a strong word. Naivety was always a big aspect of Goku's character on Dragon Ball, but he was never unwise or plainly not smart. In fact, often, a battle's victory would boil down to a smart decision on Goku's behalf, even right up until his final fight with Piccolo Jr.
However, almost immediately during DBZ's Saiyan Saga, those key qualities became exaggerated to the point of being overly eccentric. For instance, Goku spared a dangerous villain like Vegeta who promised to annihilate the earth, just off of the slim chance that he could best him in another fight one day. That is a dumb decision.
8 Goku's Origins Were Revealed
Unlike most of the entries on this list, this is actually not a bad thing but, rather, a necessary way to expand the lore of the series whilst also taking it into a completely new direction, something sequels should always do.
The original's predecessor revealed shrouded where Goku came from and why he turned into a giant ape at the full moon. Revealing him as an alien from an extinct warrior race was a bold choice that completely detours from the original, but it also was the perfect way to take the sequel and the franchise as a whole into new heights with new story potential.
7 It Changed The Original Rules Of The Dragon Balls
Since the original series, it had always been established that the Dragon Balls on earth could only be used once to revive someone back from the dead. If they died again after their resurrection, they were gone forever.
This all changed near the end of the Cell Saga. At some point after Kami's death, Dende was retrieved from New Namek and dubbed the new Kami (Guardian, or God) of the earth. In his new role, he basically rebranded the Dragon Balls to allow them to grant revival wishes as many times as necessary without limitations, which lessens the stakes of many battles when anybody can be wished back to life however many times as they like.
6 Humans Were Too Weak Because They Couldn't Compete With The Likes Of Saiyans
In Dragon Ball Z, humans are portrayed as significantly weaker than they were in Dragon Ball. Which, on some level, makes sense when the cast is bombarded by more powerful aliens. However, in the original Dragon Ball, Tien was able to defeat Goku - who, in canon, was still an alien at this point - to become the World Tournament winner.
In Dragon Ball, humans at least put up some sort of a fight against the strongest beings. Even Yamcha proved to be one of Goku's toughest challenges early in the series. By Dragon Ball Z, both are beaten in the snap of a second by enemies like Nappa, Cell, and even Saibamen.
5 The Original Characters Were Left In The Dust
More than the Dragon Balls themselves or even the martial arts that would quickly become a major part of both series, the characters were the reason why the anime and manga were a success.
However, many of those core characters that compelled fans to tune in during the original series took a backseat in minor supporting roles for Z, and in some cases, don't show up at all. It's as if Akira Toriyama became so enamored with the new toys that he stopped caring about the old ones like Tien, Chiaotzu, Bulma, Master Roshi, and Launch. In the latter case, he quite literally forgot about her, as he mentioned to Shonen Jump in 2003.
4 It Took A More Serious Tone
With its new direction for the sequel series, Dragon Ball Z was also accompanied by an entirely new tone and atmosphere than what its predecessor offered. The original series was lighthearted and, at its core, brought a lot of comedic moments to the table. Although, it briefly descended into a more serious tone when the stakes were at their highest during the King Piccolo Saga before returning to comedy.
While the comedy is still there in small spades, Dragon Ball Z focus mostly on high stakes drama 24/7 and world-altering consequences.
3 Goku Wasn't Always So Overpowered
To the original Dragon Ball's credit, despite Goku being the main protagonist, he was never overused to the point where it felt like he was unbeatable and would beat everyone in his path. In fact, there were multiple instances where Goku even lost fights but would regroup himself to either train harder or learn a powerful lesson.
Dragon Ball Z sees Goku at his most overpowered point. Goku rarely encounters a villain that serves as anything more than just a mild inconvenience. Apart from Cell, Goku beats everyone, and even then, he still manifested as a white flash beside Gohan when his son beat Cell.
2 Goku Can Fly Now Without Help From His Flying Nimbus
Coming across characters who could actually fly was something rare in the original Dragon Ball and on some level, the thought that flight was even possible was unheard of for some characters. It's such a rarity that Goku couldn't even fly unless he was riding his Flying Nimbus.
The first character to be seen flying was Tien during the 22nd World Martial Arts Tournament. That initial flight was treated as if it was truly a big deal. It does not take long into Dragon Ball Z before everyone in the cast - including Goku, who doesn't even use the Nimbus anymore after the Namek Saga - can fly, whether it's clearly established how they learned it or not.
1 It Introduced Power Levels With Scouters
Even when Dragon Ball did start to focus more on the fighting and martial arts aspects of the show, the emphasis was more so put on strategy and channeling ki rather than who was the strongest, thanks to the wise teachings from Master Roshi. That all changed when the sequel opted to put a definite number on strength in the form of power levels, thanks to Scouters.
As soon as a finite number was put on power levels, it got confusing when fans started seeing characters weaker than those with higher power levels start to beat their opponents with relative ease.