Why do they work?
Interesting visual worlds. Costumes. Choreographed dances. Carriages sailing across the wilderness.
Thoughtful dialogue. People tended to choose their words carefully back then, or at least it seems that way in these movies. Small talk is always loaded with subtext and emotion. Letter writing is a slow, painstaking art. And when people finally do talk about their feelings, it's a big effing deal.
Themes of duty, obligation and forbidden desire. What one wants to do is almost always in conflict with what one must do. You can't just marry (or sleep with) whomever you want. You can't just get a job. And if you're a member of the royal family, you're probably miserable. Money and social status rule all.
And for whatever reason, the female characters are always interesting and well-drawn.
Here are some of the ones I've been devouring lately: