Yifter gets my vote, esp. when considered relative to his peers.
How about Everett and Parilla at 800?
Skah did outkick Geb back in 93 or 94 in a 5k or two.
93 Zurich went Skah 13:04.67, Ondieki 13:05.09, Chelimo 13:05.14 and Geb 13:05.39. At the time, it was the deepest 5k ever, I think.
Also, at St. Denis in 94, Skah went 13:10.41 to Geb's 13:10.79.
Starting in 95, though, Geb went over 5 years without ever getting outkicked, I would guess.