Superman is the poster boy for overpowered characters in comics, with a veritable multitude of powers, astonishing displays of sheer strength (like bench-pressing the entire planet without breaking a sweat), and even ways to regenerate himself were he ever to be beaten, like resurrecting more than once. He's meant to look as untouchable and undefeatable as what he fights for: truth, justice and virtue.
This is all great - he's a powerful symbol of hope that makes us feel like these ideas are unbreakable and inspires us to follow in his footsteps - but it also makes the defeats by his foes feel like a heavy blow. What better way to illustrate the threat that a villain poses to humanity and all existence than defeating the guardian of all that's good?
Because of this, writers often make a point to never let our big hero be overshadowed by his colleagues when working with them in the Justice League. However, with a publication history being 18 years shy of a century (WOW) and his popularity still going strong, we've seen him at his lowest and highest, so there's no way any newer hero could be more powerful than he is, much less hanging out with him in the JL, right?
Well... let's just say that 10 doesn't cover them all.