Found this online
Stars to hold the belts.
01: Bruno Sammartino (17 May 1963 - 18 January 1971)
2,499 Days
02: Bob Backlund (20 Feb. 1978 - 26 Dec. 1983)
2,138 Days
03: Hulk Hogan (23 Jan. 1983 - 05 Feb. 1988)
1,838 Days
04: Bruno Sammartino (10 Dec. 1973 - 30 Apr. 1977)
1,541 Days
05: Pedro Morales (08 Feb. 1971 - 01 Dec. 1973)
1,027 Days
06: Macho Man Randy Savage (27 Mar. 1988 - 02 April 1989)
371 Days 07: John Cena (17 Sep. 2006 - Current Day) 366 Days
08: Hulk Hogan (02 Apr. 1989 - 01 Apr. 1990)
364 Days
09: Diesel (26 Nov. 1994 - 19 Nov. 1995)
359 Days
10: Ultimate Warrior (01 Apr. 1990 - 19 Jan. 1991)
293 Days