If you are going to compare runners from different eras, it must be apples to apples. The only basis for comparison for runners of different eras is:
1. Olympic medal performance (the most important factor), with big bonus points for a runner doubling or tripling up in one Olympics.
You can’t give points to interim world championship medals won by current runners when such championships did not exist for earlier runners. “International” cross country championship did exist earlier, but they weren’t truly international and were just not as meaningful back then.
2. World records achieved in Olympic distances (5000, 10,000, marathon) with huge bonus points for setting a WR in an Olympic race.
Getting a WRs in rabitted, planned races does not compared to doing so in the the Olympics. Piling up WRs in the one-hour run and 20,000m is bogus. Comparing absolute times (that Bekele’s 10K WR is lower than Viren’s) counts for nothing. If you do that you are saying a guy who runs 28:50, but who has never won anything, is "greater" than Zatopek. No. Drastically improve training methods, diet and fueling information, medical and therapeutic knowledge and support, financial support (ability to go pro), etc. make absolute time comparisons among runners of different eras meaningless.
This is only post-WWII (can’t compare Paavo Nurmi—to far back). And don’t bring in “alleged drug user” claims. Rumors abound for all of these runners (maybe not Zatopek ) but none was ever busted, so you can’t prove it, so don’t start.
On that basis, my rank is:
1. Zatopek
4 Olympic golds, 1 silver, with huge points for an unmatched three medal sweep in 1952 (5K, 10K, marathon)
6 WRs (5 in 10,000, one in 5000)
2. Viren
4 Olympic golds, with bonus points for two times doing the double (5K/10K) and for coming close to a triple with the marathon in 72 (fifth)
2 WR (5,000 and 10,000) with big points for the 10,000 being broken record in an Olympic 10K race (72), which has been achieve by no one else in 5K or 10K, and only by the legendary Abebe Bikila in the marathon
3. Bekele
3 Olympic golds, 1 silver, doubled up both times so bonus points
3WR (2 in 10K, 1 in 5k), never in an Olympic race
4. Geb
2 Olympic golds, never even attempted to double up, much less triple
9 WRs (4 in 5K, 3 in 10k, 2 marathon), never in an Olympic race