The two best westerns IMO are The Good, the Bad and the Ugly (1967), and Once Upon a Time in the West (1968). After those I’d watch The Wild Bunch (1969) and the other two movies in Eastwood’s “Dollars Trilogy”: A Fistful of Dollars (1964) and For a Few Dollars More (1965). An entertaining and funny take is My Name Is Nobody (1974).