WHAT! I agree that Madame Bovary is hard to get into, but it is not horrible. And the main character is brilliant, if highly flawed. It's like saying don't read Crime & Punishment because Raskolnikov isn't the nicest.
And there are good characters in Gatsby. Gatsby himself, for example. And the author of the entire novel. Daisy (and all of those people in that circle) are meant to be horrible as a juxtaposition to Gatsby (and hence why the entire novel becomes tragic).
EDIT: Clo, I agree with you on classic literature being pushed aside. My own personal belief is that the advent of television and the creation of the "ADD" generation made novels more condensed. These classical novels tend to examine numerous characters, themes, locations etc, whereas modern novels are much more focused, more streamlined in a way.