The Greco-Persian Wars were still in their early stages at this point, but it would be Xerxes, not Darius, that continued and stepped up efforts to invade and conquer the Attic Greeks.
If the Battle of Marathon had turned the other way, as many at the time expected it to and as many historians and tacticians believe it easily could and by all rights should have, the entire course of Western and even world history would have been drastically altered. Europe was built on the ideas and culture of the Greeks, particularly the Athenians. The eventual conquering of the Greek and the establishment of the Roman Empire led to the spread of Greek philosophy, art, and science throughout the then known world; if the Persians had been successful in their attempt to conquer the Greeks, this culture would most likely not have existed by the time the Romans came around. The Renaissance also depended heavily on Greek culture when it came to reestablishing scientific and aesthetic principles, and thus modern Europe (and therefore much of the Americas) grew out of the same traditions. Greek history is essentially the root of Western history, and had the Persians won the Battle of Marathon much of that history would simply have been eradicated. Even the practice of history as a field of scholarship was a Greek innovation, so ironically te outcome and significance of the Battle...
The Battle of Marathon came at a pivotal time in the world, when the Hellenistic period was reaching its height and many of the accomplishments of the ancient Greeks occurred. Those of us who enjoy the Western culture we live in can thank Miltades for his brilliant strategy, and the plain of Marathon itself for presenting an ideal battleground for the Atheninas.
References
"Background on the battle of Marathon." (2004). Accessed 3 August 2009. http://www.guilford.k12.ct.us/~rebhunj/documents/DAY6MARATHON.pdf
Foster, J. (2009). "Battle of Marathon: Greeks vs. The Persians." Accessed 3 August 2009. http://www.historynet.com/battle-of-marathon-greeks-versus-the-persians.htm
Gill, N.S. (2009). "Persian wars: The battle of Marathon." Accessed 3 August 2009. http://ancienthistory.about.com/od/persianwararticles/a/MarathonBattle.htm
Herodotus. "The Persian Wars." Histories. Accessed 3 August 2009. http://www.thenagain.info/Classes/Sources/Herodotus-Marathon.html
"The Battle of Marathon, 490 BC." (2006). EyeWitness to History. Accessed 3 August 2009. http://www.eyewitnesstohistory.com/marathon.htm
