1952: Robert Taft
1960: JFK
1968: Election gets Thrown Into House, where Humphrey Wins
1976: Henry Jackson
1980: George HW Bush(Unless some other major Republican who didnt run due to Reagan being viewed as inevitable ran)
1988: Bob Dole
1992: Jerry Brown (But Election possibly gets thrown to the House)
2000: John McCain
2008: Hillary Clinton
2016: John Kasich(I think without Trump in the race he dominates the Midwestern and the North East Primaries and Rubio still implodes at the NH debate)
I doubt Kasich would have won the nomination. Ted Cruz would have been the nominee if Trump stayed out.
1976 was with an incumbent, btw.