Honestly, no, they haven't and let me explain why.
First of all, most of the time that they re-make old movies, it's because the classic was so awesome and now that they have new special affects and abilities that they want to re-make it using all those effects and see what it's like now. We advance so quickly in this area, so it's exciting to see how much we've improved.
Secondly, the reason they make so many books/comic books into movies is because it's profitable to do so. When you already have a large fan base behind something, if you make a movie for it, then the majority of that fan base, plus people who would normally go out to the movies is going to see that movie. When something is already popular, then there's no gamble. It's ALREADY popular so you know the movie is going to be a success. There's no wondering or gambling over whether or not people will like the movie and make money off of it because it's a guarantee with it's large fan base.
I never go out and see movies, for instance. But I still go out and see all the Harry Potter movies and Twilight movies. I'm not a movie person, but I love books and the internet, so when my favorite books make it to the big screen and I get to see them acted out, I ALWAYS go. Even though I normally do not see movies ever. They successfully make money off of me when they otherwise wouldn't have.
And people who only see movies and never read books, the author gets to benefit from often. Lots and lots of people started reading the Twilight books and the Harry Potter books after they first saw the movies because the movies made them excited about it. And they wouldn't have otherwise read them.
It just makes them so much money all around and that's the main goal of any kind of business (including entertainment) in a capitalist society, so therefore, they do what they can to make the most money and this happens to be it.
I know this makes a lot of people angry, but it doesn't make me angry at all. I don't feel like entertainment has plummeted or anything because I still get to have lots of fun through it.