Stefan Kanfer gives his top five list. An excerpt:
In 1956, after a party at Elizabeth Taylor's house, Monty lost control of his car and slammed into a tree. Surgeons could reconstruct the handsome face but not the wounded psyche; he grew fatally dependent on drugs and alcohol. Bosworth argues convincingly that it was Clift, even more than Marlon Brando, who personified the postwar leading man: anxious, vulnerable, dislocated.
A memorable example of the greatness of Montgomery Clift can be seen here.