Uhh, Luke Skywalker is the chosen one. Like Yoda was talking about in #3 maybe they read the holocron wrong or whatever had the stuff about the chosen one. And Yoda and Mace Windu didn't trust Anakin and said a few things about him going to the darkside in episodes 1 and 2, and 3 untill they found out he went to the Dark Side. Windu found out when he died, and Yoda senced it, and Obi-Wan watched him kill kids on a video thing. Correct me if I am wrong.
Chris, Luke is not the Chosen One. George Lucas said himself, from his very own mouth, that Anakin is the Chosen One. Otherwise, Luke would have defeated Vader and gutted Palpatine himself.
Anakin's fall to the Dark Side does not affect whether or not he was the Chosen One. In the end, he fulfilled his destiny.