I know its all subjective, but I really feel like "distance" should be reserved for 5K and up. If that were the cut-off point, I think the top 10 guys have to be, in no particular order
1. Frank Shorter - OG Marathon Gold/Silver, Top 5 World Rank in Marathon/10K from 1970-1975, 2:10:XX marathon PR, AR in 1972 when WR was 2:09:3X. 4x Fukouka Marathon Champ, 4x US XC Champ, 2x US OT Marathon/10K Champ, 1969 NCAA 6 mile champ, multiple time US 3mile & 6mile champ.
2. Galen Rupp - OG 10K silver, OG Marathon Bronze, Chicago Marathon Champ, Boston Marathon runner-up, sub13 5k, sub27 10K time - AR 10K, 2:06:XX marathon PR (#3 US all time?), sub-hr 1/2 marathon PR, 2x US marathon champ, 8x US 10K champ, 1x US 5k champ, 1x US road 20k champ, NCAA 5k/10k champ/XC champ, US indoor 5k AR (13:01),
3. Meb Keflezighi - OG Marathon Bronze, NYC Marathon Champ, Boston Marathon Champ, 2x NYC Marathon top3, 1x Boston Marathon 3rd, 3x US XC Champ, 13:11 5k PR, 27:14 10K PR (AR for like 9 years), 1:01:XX Half Marathon PR, 2:08:XX Marathon PR, NCAA 5k champ/10K champ/XC Champ, US Marathon Champ, US Marathon Trials 2nd, US Half-Marathon Champ.
4. Bill Rodgers - 4x Boston Marathon Champ, 4x NYC Marathon Champ, Fukouka Champ, 2:09:XX Marathon PR - AR at the time, 15K AR, 20K AR, 1 hr AR, 25K AR, 30K AR, 30K world record at the time, won 22 marathons in his career, World XC bronze, US 10K road champ and road 10K WR at the time.
5. Craig Virgin - 2x World XC Champ (no other American ever won 1x), 2x US XC Champ, 3x US 10K Champ, 1x US 10K trial champ, 5k PR 13:19, 10K PR 27: 29 (US AR, world #2 all-time at time), and Marathon PR 02:10:XX in 1980s, Boston Marathon runner-up, 3x Peachtree 10K champ, 2x Bay to Breakers Champ, NCAA XC Champ.
6. Khalid Khannouchi - current US Marathon record holder w/o wind aid - 02:05:XX, one-time world Marathon record holder (for almost 4 years), 4x Chicago Marathon Champ, 1x London Marathon Champ, 1x London third, 1x Chicago runner-up. Half-Marathon PR of 01:00:XX. Road 20K World Record Holder at one-time, 2x Peachtree 10K Winner.
7. Alberto Salazar - 3x Boston Marathon Champ, 1x NYC Marathon Champ, 1x US XC Champ, 2x US XC Trial Champ, World XC Champ Runner-Up, US 10K Road Record of 28:0X at the time, 13:11 5k PR, 27:25 10k PR, 02:08:low Marathon PR in early 1980s, NCAA XC Champ, US indoor 5k record at time (#2 all time at time).
8. Ryan Hall - US Marathon record holder /w wind aid - 02:04:xx- /wwind, 02:06:low w/o wind, US 20K record holder - 59:43, US 1/2 Marathon record holder - 59:43, Boston Marathon bronze, US Olympic Trials Marathon Champ, US Marathon Trials Runner-Up US XC Champ - 12K, US half Marathon Champ, NCAA 5k Champ, NCAA XC Runner-up,
9. Bernard Lagat - US 5k Record holder (12:54), US 5k indoor record holder (13:11) at the time, 1x 5k World Champ, 2x World 5k Runner-up, 7x US 5K Champ, 4th Olympic Games 5K (tripped up by Farah or wouldve medaled) Americans Masters Records 10K (27:49) , Half Marathon (1:02:xx), likely Marathon (02:12:XX). (not including Kenya times on here)
10. Steve Prefontaine - 2x US 3mile Champ, US 3 mile/5k record - 13:21 5k PR (world 5k record was 13:16 at the time), US 6 mile/10K record - 27:43 10K PR (world 10K record was 27:30 at the time). Pre would hold US 10K record for another 5 years until Virgin broke it, 3x NCAA XC Champ, 4x NCAA 3mile/5k champ, OG 5k 4th.