Greeks, Romans, WW1 & 2. The Euros kicked the crap out of the Persians all the time.
Nope.
The battle at Thermopylae was just a side-show. The Persians won that war - and they had the Macedonians as their allies.
Later in the Sassanid-Roman wars, the Sassanids in 612 AD actually conquered Jerusalem and much of Asia Minor.