It's probably worth noting that Khan
was a rehash when they brought him back in 1982. Didn't hurt the movie one bit. Would The Wrath of Khan
have been a better movie with some brand-new threat? I doubt it.
Meanwhile, the nitpicker in me is obliged to point that that Lex Luthor did NOT appear in Superman III,
which featured entirely new villains. Didn't help that movie one bit.