This topic has been done to death in the last few weeks. Next time use the search feature on this site.
Here one thread on the topic from last October (also about the Texas “Come and Take” it flag.)
http://www.thehighroad.org/showthread.php?t=224926&highlight=greek
But 2 points about the battle of Thermopylae:
1. It is possible “molon labe” was not spoken the way it is claimed. The first history that claims it was written over 300 years later. No earlier Greek or Persian accounts mention it.
2. What the hell was the point of the 300 Spartan and the other Greeks staying behind to fight in the main pass, after the Persians found the smaller pass to get around them? After the whole Greek army delayed the Persians 3 days, killing maybe 20,000 of them, most of them retreated after they realized their enemy was going to get behind them. The 300 and some others stayed behind and were quickly wiped out the next morning. What did they achieve? The retreating Greek army made it back to Athens several days (weeks?) ahead of the Persians, so I don’t think the extra half day the lives of the 300 et al brought allowed the rest of the Greeks to escape. There were no more pinch points between Thermopylae and Athens where the Greeks would have a chance against the much larger Persian army, so they evacuated Athens and kept retreating south. The Persians burned Athens, which was the main war goal of the Persian Emperor (to revenge a town at the edge of the Persian Empire the Athenians had helped pillage and burn several decades before.) The Emperor went back home after he achieved this aim.
There were a few land battles after Athens was burned, but the decisive victories were two naval battles (won largely by Athenian ships.) These victories are what finally destroyed the Persians and saved Greece.
I believe I understand valor and sacrifice, but it does not seem like the sacrifice of the brave Spartans (and others) at Thermopylae achieved much.