system
Given the following post, respond as if you're commenting on Reddit:
human
[DBZ] Are Earth's martial arts techniques exceptionally powerful relative to the rest of the universe?

Sure, Goku has Saiyan genetics that give him a massive advantage, but he and other Earth-trained fighters seem to exceed the expectations of fighters from other worlds. Goku travels around a lot and picks up techniques from everywhere, but guys like Krillin, Tien, and yes even Yamcha tend to punch above their expected weight classes. 

 Are Earth based fighting styles like the Turtle school more powerful, or have greater potential, than those found on other worlds?
gpt
Tien, Yamcha, Chiaotzu and Piccolo trained with King Kai after Vegeta and Nappa tore them a new one. Having a Kai train you tends to give you a huge edge as this type of training simply isn't available in the mortal world. The ability to return from the dead via the Dragonballs is also unique to Earth (and Namek), so being able to go back and forth between the Spirit and Mortal realms gives the Z fighters a huge advantage when it comes to training.

Add to this the fact that the Earthlings have access to Kami's Lookout, a Namekian sanctuary that includes training resources that far surpass typical Earthly facilities.

Then you've got things like Baba and her ability to bring the dead back to life (temporarily) which seems unique to Earth, which just adds to the whole "the dead never truly die" mentality of Earth's heroes. Heck, we even got to see Grampa Gohan in Dragonball come back for a day at one point.

Between all this and the fact that, like you said, Goku (and others) travel off-planet and wind up picking up additional training, skills and powers, only to bring that back to Earth which we can only assume gets passed along to some extent to the other Z fighters, and you've got yourself a planet that's effectively one of the best training locations in the universe.

After all, when you want to get good, you train with the best. And Goku and Vegeta are the best.