In the film 300 (and the sequel), it should be borne in mind that it was based on the graphic novel rather than the actual ancient sources. While most of the scenes are VERY fanciful, elements of the film to demonstrate Herodotus (the main source for the battle of Thermopylae in the first 300 film) as a storyteller, basing his history (The greek Historia translating more accurately as 'geography') off the back of the Homeric oral tradition of storytelling. For instance although many of the fighting styles and individual elements are blatantly wrong, the character development and storytelling parts are quite good. For instance, Herodotus does claim that there were 'millions' of Persians present at the battle, which is very unlikely...

[7.184] As far as this point then, and on land, as far as Thermopylae, the armament of Xerxes had been free from mischance; and the numbers were still, according to my reckoning, of the following amount. First there was the ancient complement of the twelve hundred and seven vessels which came with the king from Asia - the contingents of the nations severally - amounting, if we allow to each ship a crew of two hundred men, to 241,400 - Each of these vessels had on board, besides native soldiers, thirty fighting men, who were either Persians, Medes, or Sacans; which gives an addition of 36,210. To these two numbers I shall further add the crews of the penteconters; which may be reckoned, one with another, at fourscore men each. Of such vessels there were (as I said before) three thousand; and the men on board them accordingly would be 240,000. This was the sea force brought by the king from Asia; and it amounted in all to 517,610 men. The number of the foot soldiers was 1,700,000; that of the horsemen 80,000; to which must be added the Arabs who rode on camels, and the Libyans who fought in chariots, whom I reckon at 20,000. The whole number, therefore, of the land and sea forces added together amounts to 2,317,610 men. Such was the force brought from Asia, without including the camp followers, or taking any account of the provision- ships and the men whom they had on board.

Similarly, Gorgo, played by Lena Headey in 300 was reputedly fairly interesting as a historical figure. In one case she discovered a hidden message on a wax tablet that no one else had been able to discover:

Gorgo, who was the wife of Leonidas, divined it and told the others that if they scraped the wax off, they would find something written on the wood underneath. This was done; the message was revealed…" (Herodotus, The Histories, 7:239.)

Pleasingly the famous line from the first film 300, "This is SPARTA" does (sort of) come up in Herodotus. The messenger, having asked for the gift of 'earth' is thrown into a pit, that would have been used for the execution of criminals:

To Athens and Sparta Xerxes sent no heralds to demand earth, and this he did for the following reason. When Darius had previously sent men with this same purpose, those who made the request were cast at the one city into the Pit1 and at the other into a well, and bidden to obtain their earth and water for the king from these locations. [2] What calamity befell the Athenians for dealing in this way with the heralds I cannot say, save that their land and their city were laid waste. I think, however, that there was another reason for this, and not the aforesaid. (Herodotus, 7.133)

I don't have time to elaborate anymore at the moment (and haven't had chance to see the new 300 sequel) but I hope this helps.