"mplatt," I'll repeat my opening "qualifier":
"In almost any situation where there is more than a small number of possible outcomes -- a marathon, a horse race, ..."
Tiger has lost a LOT more tournaments than he has won -- even when you apply the selection bias of "when he's rolling."
Most races shorter than the marathon, where Aoita, El G, Bekele et al. made/make their bones have much narrower range of possible outcomes becase there are fewer moving parts than in a marathon. Things like dehydration, or how well you handle an uphill at 21 miles on a cramping calf -- are not factors, so being a superior runner is a bigger factor than "externalities"
And yes, Geb wins all his marathons now, but they're coronations, not competitions. His past record is spiotty when he';s had to take on Khannouchi etc. This September's real-Berlin Marathon will be his first one against a genuine challenger in a long time.