They didn't complain that Luthor was showing up because Luthor is Superman's reoccurring nemesis - but as soon as people found out his plan was ripped from Superman the movie everyone cried foul.
And Superman Returns is not a movie I would willingly bring to a defense.
The team behind ST

OS transplanted from a better movie - they claim that this is their alternate universe yet they take what they want and discard the rest. Like buying the latest camera, chock full special features and tossing away the instructions.
And Khan is a reoccurring nemesis for Kirk, no?
Look, you're missing the forest for the trees. I don't begrudge anyone not liking the film or having an opinion contrary to mine. All I'm saying is that the criticism that this film "recycles" and therefore should not be considered "original" or creative in some fashion rings hollow to me.
Other franchises have re-used characters. The Joker went from comic book, to hokey TV villain, to crazy movie villain, to really crazy movie villain. So let's not pretend like simply re-using a character is an issue here. It's not. It's whether or not they used that character well. And again, if you don't think they did it well, fine. I've even said that I don't think that the character needed to be Khan for this story to work. But given that it was Khan, I felt it was a fair interpretation of the character.
Oh, he borrowed a scene from another movie? Well, Lucas lifted a sequence from The Searchers, for A New Hope (and Forbidden Kingdom). Half of any given Tarantino movie is from another movie (
at least half).
It's really ok if you didn't like the movie. All I'm trying to point out, is that some of the criticisms of the film I've read here, are things which aren't criticized in other movies. And to me, if you're going to write the film off because it re-used a character, you should disqualify yourself from watching a film like The Dark Knight.
Except, nobody in their right mind would do that, because nobody
really thinks that you should judge a film based on the premise of whether or not they re-used a character. That's just something they say because it's an easy criticism to make. The film should be judged on its own merits, rather than some selective application of completely arbitrary personal "rules."
And if you still don't like the movie, that's totally fine. Just stop being so banal about it.
tl;dr; It's ok for you to not like the movie; but
some of the reasons that
some people give, don't make sense