It's a fascinating list that can be found at:
Please read that article to see his reasoning behind his picks.
I'll list his top 12 with a few of my comments.
His top 6 is:
1. Abebe Bikila - very smart #1 pick.
2. Frank Shorter
3. Samuel Wanjiru - great to see him so high.
4. Mamo Wolde
5. Bill Rodgers
6. Haile Gebrselassie
Those six right there will certainly start a good discussion. The next 6 are just as interesting.
7. Clarence DeMar
8. Known drug cheat. I won't mention his name but I didn't like him appearing in the list or Hersh seemingly condoning his cheating by saying, "it is likely (Drug Cheat) was among the many beneficiaries of his country’s state-sponsored doping program. What is unknown is how many other marathoners worldwide also were doping in an era when it was ridiculously easy to beat testing."
9. Gezahegne Abera - remember this guy? The seemingly forgotten man. Too bad injuries robbed him of a long career.
10. Stefano Baldini-hmmmm. Ahead of Seko??? Not sure about that one.
11. Toshihiko Seko
12. Pheidippides - You might want to put him at #1 but I like his reasoning for Bikila.