Sometimes heroes retire, sometimes they fall in battle. But either way, someone has to step up to take a missing hero's place.
A brief note: All handpicked successors were wiped from this list. I exclusively picked heroes introduced as replacements for characters who were temporarily disabled who were NOT GIVEN THE MANTLE BY THE PREVIOUS HERO. So, even though I like them a lot, no Kamala Ms. Marvel or FalconCap or Wally West Flash. They're pretty great, though. But replacements only, no successors.
Honorable Mention 1: Superboy (Conner Kent)
Hey, it's one of the four replacement Supermen from the decent, but not excellent, Reign of the Supermen story arc.
Cadmus was an organization designed to work on cloning. It went pretty well, because they did clone a bunch of people, after all. And one of them was Superman.
But when he came out of the tube, he was still just a teenager. And maybe giving a nineties teen Superman-level powers was a bad idea? I mean, it worked out in this case, but nine times outta ten, you're in for a world ruled by his dictatorship Kyle and his love of skateboarding and Sunny D (all right!). But, hey, Kon-El (or Conner Kent) is a Superman clone. So he's a pretty decent kid.
Kind of a jerk sometimes, but he has potential to live up to. Oh, but only half of his DNA is from Superman. The other half is from…gasp…Lex Luthor! All right, solid twist, solid character. Although that t-shirt and jeans costume is awful. Dude should go back to the rad leather jacket.