I nominate the 1988 Breeders Cup.
Sprint - Gulch - beating Very Subtle, Precisionist and Olympic Prospect
Juvenile Fillies - Open Mind -Champion at 2 and 3.
Mile - Miesque - First two time winner of a Breeders Cup race
Turf - Great Communicator - beating a host of great ones
Distaff - Personal Ensign - beating Derby winner Winning Colors
Juvenile Colts - Is It True - beating the great Easy Goer
Classic - Alysheba - beating among others Forty Niner and Seeking the Gold
I happened to be lucky enough to be there that day. Sitting at the quarter pole, wet, cold and thrilled all day long. Personal Ensign's charge was the most hair raising, goose bump inducing race I have ever seen. Great article below on the day. Anybody got any other great days to compare?
https://www.si.com/vault/1988/11/14/...-day-of-racing