Here is my list of storms that I think may have reached Category Five at peak intensity.

Before 1928

Great Hurricane of 1780 ( 1780 )
1856 Last Island Hurricane ( 1856 )
Indianola Hurricane of 1886 ( 1886 )
1893 Cheniere Caminada Hurricane ( 1893 )
Hurricane San Ciriaco ( 1899 )
Galveston Hurricane ( 1900 )

After 1928

Hurricane Fox ( 1952 )
Hurricane Hazel ( 1954 )
Hurricane Cleo ( 1964 )
Hurricane Betsy ( 1965 )
Hurricane Georges ( 1998 )
Hurricane Floyd ( 1999 )
Hurricane Lenny ( 1999 )
Hurricane Dennis ( 2005 )

( Post would have been more meaningful if you had added your rationale for the intensity upgrades.)