I made a post on the best/worst Secretary of State, now wanting to get a feel of the best/worst Secretary of Defense from 1950-2020:
George C. Marshall (1950-1952)
Charles Erwin Wilson (1953-1957)
Neil McElroy (1957-1959)
Thomas Gates (1959-1961)
Robert McNamara (1963-1968)
Clark Clifford (1968-1969)
Melvin Laird (1969-1973)
James Schlesinger (1973-1975)
Harold Brown (1977-1981)
Caspar Weinberger (1981-1987)
Frank Carlucci (1987-1989)
Dick Cheney (1989-1993)
Les Aspin (1993-1994)
William J. Perry (1994-1997)
William Cohen (1997-2001)
Donald Rumsfeld (1976-1977; 2001-2006)
Robert Gates (2006-2011)
Leon Panetta (2011-2013)
Chuck Hagel (2013-2015)
Ash Carter (2015-2017)
Jim Mattis (2017-2019)
Mark Esper (2019-2021)
Note: I am not adding Lloyd Austin as he is new to the role.