Since the two of them first crossed paths, the debate has raged amid the Dragon Ball fandom over which is more powerful: Goku or Vegeta. Sure, Vegeta has technically defeated Goku on more than one occasion, but Goku consistently elevates his power level before Vegeta, leaving the Saiyan Prince to play perpetual catch-up. While there is room for some debate, one of the last chapters of the Dragon Ball Z era essentially states outright that Goku is better, and even Vegeta knows the true reason as to why that is.
Goku made his debut along with the series itself in Dragon Ball chapter 1, and he would go through the entire classic Dragon Ball story arc without running into Vegeta, or any other Saiyan for that matter. However, within the first few chapters of the Dragon Ball Z era, Goku is met face-to-face with Vegeta–and nothing was ever the same again. When Vegeta made his debut, he was a cruel villain who wanted to wipe out all life on Earth and then sell the vacant world to the highest bidder on behalf of his boss, Lord Frieza. However, Goku and the Z-Fighters were determined to stop him. While Vegeta proved to be stronger than Goku one-on-one, the combined might of the other Z-Fighters was too much for Vegeta, leading to his defeat and near demise. From that point on, Vegeta vowed to never be bested by the likes of the Z-Fighters or anyone else as he decided he was going to be stronger than every fighter in the cosmos–including and especially Goku.
In Dragon Ball chapter 510 by Akira Toriyama, the Earth is destroyed and humanity nearly completely wiped out after Majin Buu did what no other villain could do and blew up the whole world. The only survivors were Goku, Vegeta, Dende, and Mr. Satan–and, of course, Majin Buu himself. Those survivors were teleported to the world of the Kais and were quickly followed by Buu as the villain now hungered for the entire universe after getting a taste of cosmic destruction upon annihilating the Earth. So, using his last bit of energy, Goku powers up to Super Saiyan 3 and battles Kid Buu for the sake of universal survival–and all Vegeta can do is watch.
Vegeta Explains Why Goku will Always be Better than Him
While watching Goku fight Kid Buu, Vegeta realizes exactly why Goku is so much stronger than he is: Goku doesn’t fight to win, he fights to get stronger. Vegeta’s main goal in a fight is to defeat his enemy, which was made clear throughout the entire DBZ series as Vegeta just wanted to be better than Goku. Upon this realization, Vegeta calls out to Goku and tells him to hang in there, calling him “number one”–thereby officially admitting that Goku is, in fact, the best fighter in the universe, which means that–by extension–Vegeta is naming himself as the second best at least in an uncharacteristic act of humility by recognizing Goku’s superiority.
This whole explanation perfectly sums up why Goku reaches new levels before Vegeta on a regular basis. Vegeta needs someone to be better than, which means someone has to be the best in order for Vegeta to try and surpass them–and that someone is always Goku. For this reason, Vegeta will never truly be better than Goku within the world of Dragon Ball, and he knows it.