I don't undersand why you get so worked up when an actor is replaced by another one.
It's not a big deal.
How do you know the Iron Man character would not be as good if it was played by a different actor? How do you know the new actor who plays Spiderman will not be as good as Tobey Maguire? Based on what? You haven't seen anything yet. It is hard to make a judgement on something you haven't seen. You don't know if a new actor will not be as good as his predecessor until you see the movie.