I feel like we've had this thread before, but my answer to this question will always be "Showgirls"! It's sooooooo bad...especially when you consider that Elizabeth Berkeley actually STUDIED for her role. How can I not nominate a movie with dialogue like this:
Cristal Connors: I've had dog food.
Nomi Malone: You have?
Cristal Connors: Mmm-hmmm. Long time ago. Doggy Chow. I used to love Doggy Chow.
Nomi Malone: I used to love Doggy Chow, too!
(quoted from IMDB)
Center Stage is cheesy, too, but what do you expect of real dancers who are trying to act? The dancing in that movie is really good. Especially when you compare it to Save the Last Dance, with Julia Stiles trying to pass herself off as a ballerina.