5. Eddy Merckx (1969-72, 74)
Many still consider Merckx the greatest cyclist ever, even after the Armstrong era. In addition to his five Tour de France victories, Merckx won the Giro d'Italia five times and the Vuelta a Espana once. He won the world title as an amateur and a pro and broke the record for most distance covered in an hour. Merckx finally began to fade away in 1975, when he was runner-up in France. He raced once more, finishing sixth in 1977, before retiring.