Originally Posted by
Psyren
The whole point of "Guy at the Gym" is referring to a level of power that a mundane being can gain purely through training or self-improvement. None of the characters you listed (no, not even Goku) got where they were purely through training. It might not be called "magic", but whatever it is is still something you can't get from a gym.
It's telling that the true Guy at the Gym who achieved preternatural power - Saitama - is a joke character, which shows how farcical this very idea even is.