If every city that came in second in the final bidding results for the Olympics was the host:
1896: Athens (no opposition)
1900: Paris (no opposition)
1904: Chicago
1908: London (they actually came in second and hosted)
1912: Stockholm (no oppostion)
1916: Alexandria (cancelled due to WW1)
1920: Amsterdam
1924: Amsterdam
1928: Los Angeles
1932: Los Angeles (no opposition)
1936: Barcelona
1940: Helsinki (actually came in second and were going to host before cancellation due to WW2)
1944: Rome (cancelled due to WW2)
1948: Lausanne
1952: Minneapolis-Los Angeles (tied for second)
1956: Buenos Aires
1960: Lausanne
1964: Detroit
1968: Detroit
1972: Madrid
1976: Moscow
1980: Los Angeles
1984: Los Angeles (no opposition)
1988: Nagoya
1992: Paris
1996: Athens
2000: Beijing
2004: Rome
2008: Toronto
2012: Paris
2016: Madrid
2020: Istanbul
2024: Paris (no opposition)
2028: Los Angeles (no opposition)
2032: Brisbane (no opposition)