Who cares what actually happened? IT LOOKS COOL!!!! Any movie with Sparta, cyclop things, and rhinos kick butt, okay?! Dont dis the movie.
You're missing the point. I don't care about whether they make the spartans wear red cloaks (ironically, that sort of detail they will probably get right). I care about the fact that what actually happened, together with a bit of legitimate filling in of gaps from imagination, is a FAR more exciting story than Leonidas as some sort of Iron Age Batman going toe to toe with Xerxes done up as every cartoon baddie you ever saw. Boring. Seen it before. Its not the historical failure that's the problem, its the dramatic failure.

For god's sake, this was a king, bound up in a rigid honour code, going to his death far from his land, in large part for the benefit of a city he at best disliked. His eventual death is (as the story goes anyway) the result of a betrayal. How can you NOT make a great story out of that? I don't know, but Frank Miller sure does.

If they want to make a fantasy movie with spartans, rhinos and cyclops as well, that is fine by me.

Incidently, if you are at all interested, or you just want a very interesting and very exciting read, get Persian fire by Tom Holland. Its not a novel, its history. But if you don't finish it in one sitting once the persian armies start marching on greece then you have no soul.