On the topic of Green Lantern: There have been at least 4 that I know of (on Earth-- there are many others on other worlds)
On the topic of the FF movie: It wasn't canned because it was bad, but because just as it was nearing completion another director (I believe it was Wolfgang Peterson) decided he wanted to do his own version. They canned the one being worked on in favour of a big-budget one, which never manifested.
Regarding Superman and Batman: There are a few projects in the works. There will be a new Superman movie (Anthony Hopkins will play Jor-El) and a Superman vs. Batman movie. There is also (supposedly) an adaptation of Frank Miller's Dark Knight Returns as well as Batman Beyond.