Let me know if I am too cultural, but what the hell.
If Leonidas met Cyrus, what would happen?
Leonidas: If I could defeat your grandson, I could defeat you!
Cyrus: It's on, you cur!
You mean one on one? There are too many factors. What armor? What weapons? Are they on foot or mounted? Does Cyrus have a chariot? Where are they fighting? Answer these questions, and then I can make a decision. Right now I'm thinking Leonidas, since ALL Spartans were physical fitness freaks and trained extensively to hone their skills. In the Greek society, the rich and powerful didn't stop that "hard" work when the assumed their high positions. But I'm will to bet Cyrus won't be used to fighting against anyone: he's used to staying far back, directing troop movements as a general. Depending on what factors you give Cyrus, I say Leo takes it.
This fight is a military one.
Although this is off topic, this video made me chuckle, because I got a kick out of it:http://www.youtube.com/watch?v=Stn2PpAhpqw&feature=related