John Wesley Harding wrote:
I think this is a reasonable approximation of the top-20:
1. Frank Shorter - Probably the 3rd “greatest” marathoner ever after Kipchoge and Bikila and has an unprecedented legacy in U.S. distance running
2. Jim Ryun - 3 Olympics including silver in ‘68, achieved almost rockstar status from ‘65-‘67 when he was the best mid-D runner in the world and lowered WRs at 880y/1500/mile
3. Bernard Lagat - Standing AR-holder at 1500, 3000 & 5000, 5 WC medals (2 gold) & 3 Olympics while representing U.S., nearly unbeatable domestically from ‘05-‘16
4. Galen Rupp - 4-time Olympic qualifier and 2-time Olympic medalist, PBs of 3:50.9i/7:30.2i/12:58.9/26:44(AR)/2:06:07, best U.S. 10k man ever (sorry Billy Mills)
5. Mal Whitfield - 2 x Olympic gold in ‘48 & ‘52, 5x #1 rankings from ‘48-‘53, won 66 of 69 races at 800/880y from June ‘48 through ‘54, 1:47.9 PB in ‘53
6. Bill Rodgers - Won Boston and NYC 4x each between ‘75-‘80, ranked #1 in ‘75, ‘77 & ‘79, collected wins in Amsterdam, Fukuoka, Toronto, Houston, Stockholm, etc., 2:09:27 PB in Boston ‘79 made him #4 AT
7. Johnny Gray - Record 11 top-10 rankings from ‘84-‘96, 4 Olympic finals earning bronze in ‘92, broke 1:43 in 4 seasons, 1:44 in 11 seasons and ran 1:45.50 or better in 18 straight seasons, 1:42.60 PB made him #4 AT in ‘85
8. Matt Centrowitz, Jr. - Perennial world and Olympic finalist, winning Olympic gold in ‘16 & lesser WC medals in ‘11 & ‘13, PRs of 1:44.6/3:30.4/13:00.4
9. Steve Scott - Ranked #1 in U.S. at 1500/mile 10 times and ranked top-10 in the world 11 times, earned silver at the ‘83 WC and missed his best chance at an Olympic medal due to the boycott, held mile AR (3:47.69) for 25 years and broke 4:00 more than anyone in history
10. Meb Keflezighi - 4-time U.S. Olympian taking silver in the marathon in ‘04, former 10,000 AR-holder (27:13), major marathon wins in NYC ‘09 & Boston ‘14
11. Khalid Khannouchi - At one time held 3 of the 4 fastest marathon performances (2 as a U.S. citizen, including the WR), still holds AR at 2:05:38, won London (‘02) and Chicago 2x (‘00, ‘02) for the U.S.
12. Craig Virgin - 3x Olympic qualifier missed his best chance for a medal due to the 1980 boycott, former 10k AR-holder at 27:29 which made him #2 AT ca. 1980, his greatest achievement is winning world XC in ‘80 & ‘81
13. Steve Prefontaine - AR-holder at every distance from 2,000-10,000 at the time of his death, very tough to beat domestically from ‘71-‘75, heartbreaking 4th at ‘72 games, immortalized legacy
14. Ryan Hall - Fastest American marathoner under any conditions (2:04:58, Boston ‘11) & #3 officially (2:06:17), 2-time Olympian, 4 x U.S. #1 marathon rankings, AR-holder at 1/2 marathon (59:43)
15. Billy Mills - Surprise Olympic gold at 10,000 in ‘64 in Olympic record time, went on to set 10k AR (28:17) and tie the 6-mile WR (27:11) in ‘65
16. Alberto Salazar - Former 10k AR-holder (27:25), ranked world #1 at the marathon in ‘81 & ‘82, won NYC 3x (‘80-‘82) and Boston ‘82 with CRs at both, ran 21” under the WR in NYC ‘81 which proved ~148m short
17. Dathan Ritzenhein - 3-time Olympian, former 5,000 AR holder, bronze at 2009 world 1/2 marathon champs, PRs of 12:56.2/27:22/60:00/2:07:47
18. Bob Kennedy - 2 time Olympic 5k finalist, former AR-holder at 3k (7:30.8), 2 mile (8:11.6) and 5,000 (12:58.2), 9x #1 U.S. rankings at 5,000
19. Sydney Maree - Former AR-holder at 1500 (3:29.77), mile (3:48.8), 3,000 (7:33.4) & 5,000 (13:01.1), placed 5th in ‘88 Olympic 5,000, #2 AT at 1500 & #3 at 5,000 ca. 1985
20. Bob Schul - Had an amazing year in 1964, going undefeated outdoors while setting the 5,000 AR (13:38) and the 2 mile WR (8:26.4) and winning Olympic gold with a stellar kick, won the ‘65 U.S. 3-mile champs in 13:10 AR before retiring from injury
Wottle, Symmonds, Solinsky and Jager would be among the next up.
Great list. I'd put Pre a little lower and Mills and Schul a little higher.