Komen was sick, but wasn't at the same level as the other guys for long enough plus he only has one world championship gold versus several world and olypic golds for Geb and Bekele. So we eliminate Komen.
Replacing Komen with El Guerrouj makes more sense. El Guerrouj totally dominated the 1500/mile, losing only 3 races in 8 years. However, he didn't have the range of the other two. He really focused only on the 1500/mile, moving up to the 5k only at the end of his career (though he did have a lot of sucess winning world silver and olympic gold). He also never ran cross country like Bekele, and his career was much shorter than Geb's.
Geb and Bekele both were amazing on the track. Geb has 9 world outdoor or olypic medals, Bekele has 10. Geb had a bit more range, his indoor 1500 PB is faster than Bekele's outdoor 1500 PB, has the marathon WR, and he also won world indoor gold at 1500. Bekele dominated cross country (12 gold inclucing 1 junior), while Geb only managed 1 bronze. Indoors however, Geb has 4 world gold compared to Bekele's 1. All together Gebrselassie has set 27 world records while Bekele has only set 4.
Bekele may end up competing for another 10 years and eventually anihilate the marathon world record, but at this point I have to give the edge to Geb simply for longevity, range in distance and total body of work. It is very likely that one day we will all unanimously look at Bekele as the greatest of all time, however at his moment that title belongs to Gebrselassie.