Pre was considered great in the USA. He did do it all here. American records, college wins, AAU wins. He was a legend for most other runners of that era.
He was not even on any list outside the USA as one of the all-time greats.
When talking about all time greats, time does not really matter - especially in the era of drugs. You really don't know which records (or wins for that manner) are drug assisted. All you guys that have this time obsession are people who never won many races. You're races considered of running PR's, but finishing in the middle or back of the pack. GOAT win race, first and fore most. World record are a bonus, bur not required.
What you can compare is how much greater you are than you peers. The best way to determine that is by Wins. In particular, wins in major events.
Cross country does not matter. Not everyone peaks for it or tries to be their best. It's just part of training for most. What matters is Olympic games and World Championships. In that order. On top of that multiple wins in a single championship trumps single wins. Winning the 5 & 10k in one year is, IMO, better than winning them in two different years. Both Geb and Kenny had problems with that.
If Mo can win the 5k here, then come back and win the 5/10 in 2016, then he has a good case.