My opinion which undoubtedly reflects my cultural bias:

==== B.C. ====
753 founding of Rome and the birth of an empire
490 battle of Marathon preserves Greece and stops eastern expansion
486 birth of Buddha and one of the largest religions in the world
323 death of Alexander marking the end of the Greek period and its contribution to western culture.
==== C.E. ====
29 approximate death of Jesus Christ and birth of Christianity
622 birth of Islam as a religion
800 Charlemagne crowned emperor of the western empire
1066 Battle of Hastings and the start of English world dominance
1455 Gutenberg's printing press is used
1687 Newton publishes "Principia Mathematica" and modern physics is born
1776 United States declares its independence
1804 Napolean is crowned Emperor
1859 Charles Darwin publishes "Origin of Species"
1903 Orville and Wibur Wright first flight
1905 Einstein publishes the theory of Special Relativity
1945 First use of atomic weapon
1959 First integrated circuit is invented
1961 Gagarin is the first man in space
1969 Neil Armstrong walks on the moon
1991 The lowering of the Communist Flag marking the final end of Soviet Republic

I think the importance of 11 Sep 2001 is yet to be proven.

-V