Seen a few real good ones live. My two favorites, both Marlboro Cups (I miss that race a lot):
1976 Marlboro Cup:
http://www.youtube.com/watch?v=hWeWHgHivWk
Forego runs down Honest Pleasure.
1978 Marlboro Cup:
http://www.youtube.com/watch?v=RBHczmcKS5M
Seattle Slew (2-1) dominates Affirmed(1-2) in the first-ever race with two Triple Crown winners.