I always liked Olivia de Haviland (sp?) in those movies with Erol Flynn, especially “They Died with Their Boots On”. Not sure if that is considered “sexiest”, but I liked her looks and the roles she played. (Robin Hood, etc.)
In Gone with the Wind, I thought Olivia was MUCH hotter than Vivien.
Melanie was a real woman. Which is always much sexier than a self-absorbed bimbo like Scarlet.
She was beautiful in To Each His Own.