Goku is a Saiyan who was raised by a human and now has a family of his, as shown in the record-breaking anime, Dragon Ball Z. His overpowered strength is the stuff of legend among anime fans. He is a martial artist who has gotten so strong, that he’s accomplished feats that went unmatched for over 1,000 years. He has become the protector of Earth, defending the humanity countless times from dangerous conquerors. If Goku was born a human, it is highly unlikely he would become the Super Saiyan god fans have watched him grow into, but what feats could he still achieve, especially when compared to his human friends and partners?
Considering what Raditz was able to achieve as a Saiyan, which we saw in the fight against Goku and Piccolo, we can deduce that a low-tier Saiyan can simultaneously defeat both a human and namekian. However, Goku is not a low-tier Saiyan and is arguably the strongest Saiyan to ever exist, so we should compare his feats to that of a top-tier human such as Krillin, Master Roshi, and the part-alien Tien. (Sorry Yamcha and Yajirobi.)
Master Roshi is the leader of the Hermit School, a martial arts dojo, and lives on a beach with a turtle and a pig. He is also the trainer of Krillin and Goku. He created the Kamehameha wave and notably used it to destroy the moon while battling an Oozaru-powered Goku. Oozaru gives Saiyans a huge boost to their overall power level, with the manga stating it provides a boost that is 10 times the base form of the user. To destroy the moon is no easy feat, which makes Roshi one of the most powerful humans alive. His disciple, Krillin, undoubtedly learned from him.
Krillin started out as the rival of Goku, with the two creating a very special human bond. Krillin is Goku’s closest ally and confidante who also studied under Master Roshi and participated in the recent Tournament of Power with them. He has also mastered the basic Kamehameha wave, as well as other useful techniques that he uses to battle the strongest opponents. Specifically, he uses the Destructo Disk, his signature move that can slice through any person, as stated during the fight against Nappa and Vegeta. He also possesses the Solar Flare technique, a move he learned from his friend, Tien, and causes the opponent temporary blindness. He famously used this move to escape from Cell, a feat even the Androids could not handle.
Tien is a fighter from the “Crane School” and is a former rival of Goku, like many characters in the series. He is one the Earth’s strongest fighters and is a member of the Z fighters alongside Goku, Vegeta, Krillin and others. He is also a descendant of the three-eyed people, so that makes him part alien and not fully human, although this heritage hardly offers him any definitive skills, save creating a myriad with his third eye. His special moves include the “Solar Flare” technique, the Kamehameha wave, and his signature Tri-Beam move, which he famously used to hold Cell off in episode 153 of Dragon Ball Z.
Tien, Master Roshi and Krillin fought in the Tournament of Power and showed they could hold their own against some of the strongest fighters in the 12 universes of Dragon Ball. Krillin also survived his battle against Super Saiyan Blue Goku, a form that is close to one million times stronger than his base.
Since these are what the best of the humans could do, it is safe to say that Goku would at least be at their levels if he was not born a Saiyan. With his superpowers, he can battle Beerus, the God of Destruction, move faster than someone stopping time, as he did in his fight with Hit, and survive a planet explosion, which happened when he battled Majin Buu. As a human, Goku would most likely be on the level of, or slightly above Krillin, especially since the latter has shown time and time again that he would much rather raise a family than be a warrior.
According to the anime, in episode 45, Vegeta, while battling Cui, states that after his near-death loss against Goku, his power level grew by 6,000. Saiyans heal faster as well as grow exponentially stronger and quicker than humans. Krillin shockingly was the stronger of the two back in training school judging by the original Dragon Ball series, but the gap between them now is beyond description. Goku as a human obviously won’t have these advantages and would be a decoy or first-set fighter, serving to weaken the foe before the stronger warriors step in.