For me, its Steve Prefontaine. He put distance running on the map along with others. I'll never forget his will to win. Others may have had more talent but "Pre" never failed to give his very best. http://www.prefontainerun.com/
ditto on carl lewis. was thinking thorpe, but lewis dominated at a much more competitive time if you accidentally left out the "field", i'll change mine to sergei bubka.
I'm gonna agree with you on this one. For a long time, he held virtually every American distance record (he may even still own some). He would've certainly broken the 5000m world record had his life not been cut short. He's definitely idolized by many a distance runner in this country. "To give anything less than your best is to sacrifice the Gift." - Pre