Honestly, they don't really deserve the idolization they get even beyond the movies. Sparta was a rather brutal slaver society after all, the reason for their famous military training was mostly to deal with rebellion by their slave population which greatly outnumbered them. If they still existed as they did then, they'd probably be viewed with the same kind of contempt we view places like North Korea.
Zizek's take on 300 is so good, here's an excerpt:
it is the story a small and poor country (Greece) invaded by the army of a much larges state (Persia), at that point much more developed, and with a much more developed military technology - are the Persian elephants, giants and large fire arrows not the ancient version of high-tech arms? When the last surviving group of the Spartans and their king Leonidas are killed by the thousands of arrows, are they not in a way bombed to death by techno-soldiers operating sophisticated weapons from a safe distance, like today's US soldiers who push the rocket buttons from the warships safely away in the Persian Gulf?
Furthermore, Xerxes's words when he attempts to convince Leonidas to accept the Persian domination, definitely do not sound as the words of a fanatic Muslim fundamentalist: he tries to seduce Leonidas into subjection by promising him peace and sensual pleasures if he rejoins the Persian global empire. All he asks from him is a formal gesture of kneeling down, of recognizing the Persian supremacy - if the Spartans do this, they will be given supreme authority over the entire Greece. Is this not the same as what President Reagan demanded from Nicaraguan Sandinista government? They should just say "Hey uncle!" to the US..