Geb is there of course but it is always difficult to compare runners from different eras. As to the claim that there were not as many races I submit that Paavo Nurmi in 1925 ran 55 races in the US and won 53 of them... not a bad record eh. His Olympic exploits are already listed here but here is a list of record that he held at one time or another... talk about range there Records in every distance from the 1500 up to 20K something not even Geb can claim, also not that many are not in Olympic years - I have a tough time choosing someone over another being a Geb fan myself. I find Nurmi's range and revolutionizing way to be inspiring and that does not even include Zatopek who was just a horse. Anyway here are the stats for your pleasure...
EVENT RECORD VENUE AND DATE BROKEN BY
1500 m 3.52,6 Helsinki 19 Jun 1924 (Otto Peltzer Germany 1926)
Mile 4.10,4 Stockholm 23 Aug 1923 (Jules Ladoumègue France 1931)
2000 m 5.26,3 Tampere 4 Sep 1922 (Edvin Wide Sweden 1925)
2000 m 5.24,6 Kuopio 18 Jun 1927 (Eino Purje Finland 1927)
3000 m 8.28,6 Turku 27 Aug 1922 (Edvin Wide Sweden 1925)
3000 m 8.25,4 Berlin 24 May 1926 (Paavo Nurmi 1926)
3000 m 8.20,4 Stockholm 13 Jul 1926 (Janusz Kusocinski Poland 1932)
2 miles* 8.59,6 Helsinki 24 Jul 1931 (Donald Lash USA 1936)
3 miles* 14.11,2 Stockholm 24 Aug 1923 (Lauri Lehtinen Finland 1932)
5000 m 14.35,4 Stockholm 12 Sep 1922 (Paavo Nurmi 1924)
5000 m 14.28,2 Helsinki 19 Jun 1924 (Lauri Lehtinen Finland 1932)
4 miles* 19.15,4 Viipuri 1 Oct 1924 (Janusz Kusocinski Poland 1932)
5 miles* 24.06,2 Viipuri 1 Oct 1924 (The last officially approved WR; unoffic. G. Pirie GBR 1953)
6 miles* 29.36,4 London 8 Jun 1930 (Ilmari Salminen Finland 1937)
10 000 m 30.40,2 Stockholm 22 Jun 1921 (Ville Ritola Finland 1924)
10 000 m 30.06,2 Kuopio 31 Aug 1924 (Ilmari Salminen Finland 1937)
15 000 m* 46.49,6 Berlin 7 Oct 1928 (The last officially approved WR; unoffic. V. Iso-Hollo FIN 1936)
10 miles* 50.15,0 Berlin 7 Oct 1928 (Viljo Heino Finland1945)
20 000 m 1.04.38,4 Stockholm 3 Sep 1930 (Juan Zabala Argentina 1936)
One hour race 19 210 m Berlin 7 Oct 1928 (Viljo Heino Finland 1945)
4x1500 m 16.26,2 /TuUL** Stockholm 12 Jul 1926 (TuUL Finland 1926)
4x1500 m 16.11,4 /TuUL** Viipuri 17 Jul 1926 (Great Britain 1931)