[Fashion Zombie]

Haha, Gerard Butler is Scottish. Maybe when he played Leonidas he hadn't finished the accent portion of Acting 101?

But yeah, I think the accent thing is just because its one common accent that's easily decipherable by most of the people that know the English language. Also, sometimes I think if we're not familiar with the accent from a region, it can come across as an accent we're more familiar with. And in the end, who really knows what kind of accent the ancient Romans had? So I guess its all in the director's artistic choices and the viewer's interpretation.