The industry is so plastic that there has been much borrowing. This isn't unique to comics as any fan of the blues or Shakespearean theatre can tell you.
Apart from recycled plot lines and 'surprise' endings, even the names of characters and the powers they possess have been given regular reworkings.
Much of this is, as we have seen, as a result of the Silver Age retooling of Golden Age characters. This applies to both Marvel and DC and is handled differently according to the status of the character but also considered is their origin, their costume, their powers or traits. Changing the character from an alien to an android may reflect changes in times and technology as much as a desire to make the character 'better'.
The iconic characters had to be brought across whole while the characters further down the totem underwent more radical changes to their identity.
I suppose when Stan Lee was borrowing from the past, he was just as happy to snaffle up something from some other company to use as his own as he was to draw from Timely sources. But the appropriation of licensed companies by DC has seen them also offering different treatments to the Archie/Red Circle group of superheroes (who are undervalued in my opinion)and Charlton as well
Certain names recur quite separate from straight revamps. We have a couple of unrelated characters named Catman and there's obviously something irresistible about the name Captain Marvel:
- the Big Red Cheese
- the gruesome character whose power is for his limbs to fly off
- Mar-Vell at the uses of Rick Jones
(One of the iterations of Captain Marvel was a black woman...)
(or if that's too disparate and confusing, there's a scholarly take that looks at all CM manifestations)
and the other name to remember is Power Man
- Rip Regan
- the Down Under Power Man
- Power Man (UK)
- the Marvel villain
- Luke Cage
- Powerman/Powerbolt (Nigeria)