My instinct is to defend the fans - the fans, after all, keep something going, and preserve it in memory, and ultimately, they are fans because they LOVE something, and that is not something to sneer at. Popular culture has the attention of a mayfly, but fans are immortal and indivisible.
That said, I just do not understand fan reaction to this film. Here we have a film that looks to have everything one would want from a Superman movie excepting possibly Kandor and giant robots, and the response is suspicion.
It's easier to criticize than to praise; if you're enthusiastic people make fun of you but if you're critical it makes you seem more "worldly" and sardonic. This is the same principle behind most movie critics; they think they sound "smarter" bashing a film, so that's what they do. In other words, the "opinions" people give at these sites may be nothing of the kind; it may just be mere posturing and puffery based on what they think smart people are supposed to sound like. And there are also always the guys who say something just to upset everyone. It may or may not be what they truly believe, but it's enough to stir the stick and that's all they want.
What is offensive about movie critics is not that they say that they DISLIKE films, but that they find unworthy films to lionize.
There is definitely an "Emperor's New Clothes" mentality around movie critics with regards to movies like TITANIC and COLD MOUNTAIN, sentimental schlop that critics, if they were being honest, could not possibly have been won over by. They fear that if they gave an honestly bad review to a film, they would be impugning their own ability to function as critics, the one thing that gives their opinion any kind of weight: their professional reputation. "He said TITANIC wasn't great, so what kind of critic is he?"
Lest everybody think I'm getting off topic, one can say that the same thing is ALSO true of comic book critics. NotSuper once asked why I disliked WATCHMEN, and I owe him a much more complete explanation I'll have to type later. But my point is this: there are some works in comics you are just not allowed to dislike, which is vexing because you can't express your honest opinion - a different matter than just sheer contrariness.