Well, I too am a native of Conyers, Georgia, and I just want to say right here that Holly Hunter’s accent makes my teeth hurt. I’ll admit that I watched too much TV and have lived in California for too long so that my accent’s been completely leeched away, but I know that I never talked like that, and never met anybody else from GA who talked like that.
But for Raising Arizona, all the accents were dead-on perfect. Especially hers. I don’t think they were going for realism at all with that movie; I think they were just going for super-emphasized “white trash.” (“Gotta git that dip-tet, Hi!”)
I agree 100% with whoever said that fake southern accents in movies are almost always awful. It offends me the most when the actors are really from the south. Watching “Designing Women” is doubly torturous, because not only is the writing so bad, but the actresses all sound like a community theater production of “Crimes of the Heart.” The only one who sounded “right” to me was Jean Smart, who was the only non-southerner in the cast.
Also spectacularly bad at being southern: Kenneth Brannagh in Wild, Wild West. Anyone in Steel Magnolias (see above, and I’m looking at you, Julia Roberts). And like others have mentioned, anybody who uses “y’all” to refer to one person.
On the other hand, I was impressed with Jodie Foster’s southern accent in Silence of the Lambs. It was too overdone to be accurate, but it worked for the part and it was believable. For accuracy, I was most impressed with Natasha Richardson’s southern accent in Nell. That is what every non-rural Georgia native I’ve ever met sounds like.