Good thread, being an old git, I forget that many fans to the sport don't know much pre-Lance.
For me:
The 1980's were a particular highlight (Hinault v Lemond, Fignon v Lemond, Millar, Roche and the Colombians).
1990's - Pantani acceleration on the climbs, Boardman's prologues, 94 Tour stages in Brighton and Portsmouth (meeting the likes of Indurain, Lemond, Chiappucci, Yates) - acknowledge this race included a young Armstrong riding in World Champions jersey IIRC.
Old films of the great classy riders of the 40's, 50' and 60's, especially Coppi and Anquetil.
But, of course, one giant, towering above all others, the man that my dad used to constantly talk about when I was a little kid, the one, the only....
Eddy Merckx, greatest rider of all time, bar none.