From the time fans learned of Goku’s official origin story within Dragon Ball, he was immediately compared to Superman–and rightly so–as both character origins are eerily similar to a certain extent. However, while Goku may be considered Dragon Ball’s version of Superman to some, Dragon Ball actually already has an official Superman ‘variant’ who has absolutely no connection with Goku.
Kakarot aka Goku is a Saiyan from Planet Vegeta who was sent to Earth as a baby just as his homeworld was on the verge of total annihilation. Similarly (and originally), Kal-El aka Superman is a Kryptonian from Planet Krypton who was sent to Earth as a baby just as his homeworld was on the verge of total annihilation. Based on their origin stories alone, it is easy to draw a comparison between the two characters–but it doesn’t stop there. After each respective alien made a life for themselves on Earth, they both became the greatest heroes their Earths had ever seen and even joined/formed a superhero team whose duty it was to protect the planet from domestic and intergalactic threats alike. Basically, due to their many similarities, Goku would have fit the bill as Dragon Ball’s Superman without question–if it wasn’t for the fact that ‘Superman’ already exists in the Dragon Ball universe.
In Dragon Ball Chapter 82 by Akira Toriyama, Goku, Bulma, and Krillin are being pursued by a Red Ribbon Army general known as General Blue who is hellbent on capturing them and taking the Dragon Balls they collected. During his villainous mission, Blue is successful in stealing the Dragon Balls from the group of child adventurers and he makes his escape back to the Red Ribbon Army headquarters. However, his escape was not a clean one and Goku was chasing after him at an incredible speed. So, Blue attempts to hijack the vehicle of some random citizen, only the car he tries to steal doesn’t belong to just anyone–this car belonged to none other than Suppaman.
Upon Suppaman’s debut, the hero was dressed as his human alter ego complete with a suit, greased black hair, and thick-frame glasses. Basically, he looked suspiciously like Superman’s alter ego, Clark Kent. Then, once he realizes that General Blue is a bad guy that needed to be stopped, Suppaman ran into a nearby phone booth and changed into his superhero costume–a trope that is widely associated with the original Superman. However, once he challenged General Blue, Suppaman lost all credibility as a worthy variant of Superman as he gave up immediately after learning exactly how impossibly strong Blue really was, and even allowed the villain to take his car without so much as throwing a punch.
While Suppaman is quite literally Dragon Ball’s Superman, he is more of a parody of the DC hero rather than a separate incarnation. However, whether he’s a joke or not, Suppaman is an established character within Dragon Ball lore and therefore has more of a claim to the title of that universe’s ‘Superman’ over Goku despite the Saiyan’s many similarities to the Kryptonian hero.