Yes, which is all very exciting in a low-life, uneducated way but wouldn't really work in real life. First of all, having lived in Greece I should tell you it was Not Leonidas and his 300 but Leonidas, his 300, and about 10000 other soldiers whohelped him in the battle. Anyhow, you can see that 300 Spartans went up against 50000 persians and lost. Obviously. Might I add here that though Spartans were raised to become killing machines, there were only about 800 of them.
Achilles, on the other hand, had the might of Ancient Greece at his disposal; you see, unlike the Spartans who were totally unsociable the Myrmidons( because that's how its written) had always sought to establish allies all over Greece. So it would be 100000 soldiers against 1000 spartans. that's 100 myrmidons for 1 Spartan. Leonidas would be DOOMED.

Well, the movies were actually as fake as it gets. But again, Spartans lost after confrontingthe full persian army. Spartans were 300. Myrmidons were about 30000 alone. The logic is that 300 against 30000 loses every time. No matter how heroic the spartans were, Achilles was immortal except from his heel of course. Spartans were simply human.

Well, excuse me but I thought the throwdown was all about how 300 guys could beat 30000 ones. Anyway, the Spartans were outnumbered to say the very least. I am not saying that they could not beat the crap out of any passer by, but it would be simply impossible to beat the crap out of 100 people at the same time.
And come on, he wasn't that arrogant. Confident perhaps? I mean he was half god, and he did have an army that was feared by most. The issue here is numbers.