okay so to elaborate a little more on this topic because it's an awesome one
1) I know there are many differing opinions as to what constitutes a "distance" event and therefore runner. Some people think it starts at the metric mile (1500m) and other believe it starts at the 10000m. For me the 800/1500/3000 are middle distance events and true distance events start at 5000m. Everyone is fully entitled to their opinion but obviously, for the sake of my previous list, it discounts El Guerrojou and Komen as their resumes are boosted by their ability at 1500m/mile/3000m. Just one olympic title, one world title and one WR (as awesome as this is) at the shortest "distance" event can't get you in the top 5 unfortunately.
2) Drugs. Well sadly we can't just omit this white elephant but for the sake of the list I assume everyone is clean even though I agree with some posters that this simply isn't the case. Would I bet my house that even one of the guys I named in the top 5 had never touched a PED in their lives ever? Come on man.
3) Best performance? I don't disagree that the recent WR of Kipchoge might be the singular best performance from my top 5 but I am not 100% certain that I couldn't make a case for either of Bekeles 5 and 10 records being equally impressive and out of reach for the foreseeable future. Only Barega this season has offered any sort of hope that someone could even approach 12.37. Even if I would go along with 2.01.39 being the singular best, the package of 12.37.35 and 26.17.53 in my opinion is equal to it for this arguments sake
4) @commenter - again this was the most difficult decision on my list - Mo at 3 and Kipchoge at 4 or vice versa. Hard because of the above point about singular best performance or which Mo doesn't even get on the radar compared to anyone on the list (funnily enough apart from the 1500m which doesn't count for my ranking purposes - see 1)). But running is not just about the clock. The Olympic Games gold medal is not awarded to simply the fastest athlete in each event for the calendar year. Winning counts and Farah is a great a race winner as there has ever been over 5 and 10000m in any era of the sport. He is basically undeniably a greater winner over these distances than Bekele. Over the span of 8 years there are only two 5000m/10000m races he DIDN'T walk away with the gold medal. That is worth more than I think popular consensus gives him. I personally think it is astounding. I have no problem with seeing Kipchoge 3 and Mo 4 but in my opinion Mo gets the nod by a 100th
5) Finally, 5th spot was also tough. Vipam mentioned Ngugi and Ngugi could possibly have a case to rival Tergat in this spot. Both won 5 World Cross races when it just the long race and Ngugis olympic gold is a huge, huge factor. But lest we forget Paul Tergats bid for an Olympic Gold medal was part of still to this day the greatest 10000m finish of all time and was thwarted by 9/100ths of a second to the man 2nd on my list. He walked away with 5 silver medals over 10000m on the track - 4 of them again, thwarted by Gebrasalasie who many thought at the time would be difficult to supplant as the greatest the world ever saw. Throw in a 10000m WR (Ngugi never really threatened the WR in any event - I guess maybe the 10000m where he was 3 seconds out) and the 'thon WR and actually the more I think about it the clearer the gap is between Tergat and Ngugi + anyone else.
Fun debate though - wondering if anyone else has an opinion with some facts and figures to back it up!