Well, the Greeks thought otherwise. (I am really stubborn).
That is the point, self-sacrifice, all such things rose the Greeks morale and so they fough gloriously. In the end Persians were defeated. And there were traitors amongst Greeks, maybe the Spartans and Thebans had held on for longer then. And they killed enemies. There were about 2,000 dead Greeks for 20,000 dead Persians. About 97% for Greeks and 12% for Persians perhaps that is (not countign the fleeing Greeks; only Thebans and Spartans).