I'd vote for...1964 Tokyo Olympic marathon! I mean, c'mon! We had Heitley as former world record holder, we had Kilby who was also former world record holder, we had Buddy Edelen also former world record holder, Terasawa who broke Abebe's old world record... Then we had Mills who upset 10000m only a week earlier and Clarke, perhaps the greatest distance runner of all time; then Hogan was Empire Games champ or European champ; Julian who won pre-Olympic Tokyo marathon.... They were ALL in the race and pretty much ALL of them at their prime! 64 Tokyo and Abebe--hands down! ;o)
Now that was a tricky answer! LA vs. Munich... I'd actually opt to pick LA. I think the depth of that field was pretty incredible. I actually don't care too much about times and how many have run sub-2:10; but just simply that field was pretty incredible; I mean, the quality of athletes--and I don't think we've matched that since. Wouldn't say that Munich was weak. I mean, it's easy to say so many ran sub 2:10, but, as Steve would know, Munich was still pre-high-tech shoe era. The shoes those guys were wearing were pretty primitive. And for them to be running 2:12 or so was pretty good. People weren't training like Seko or Dixon or Salazar or Deek back then either; they all had 8-hours-a-day work, unless you accept to live on food stamps. The athletes they had in the Munich field was classic; I don't care what anybody said about Clayton and Hill over the hill (ahhh!), those two were the history's first two sub 2:10 guys. So-and-so was over the hill or so-and-so was injured or not at his peak is kind of weak excuse. At LA, I don't think none of the actual favorites, Dixon, Seko, Deek and Salazar was at their peak; they screwed up their peaking one way or the other. But that wouldn't weaken the depth of the field. I feel Munich was probably the last of the greatest "amature" field assembled. That was sort of the last of the innocence--coincidentally, of course, the Olympic innocence was shattered at Munich.
I'd give the wishy-washy way of "selecting" and say, yes, LA was probably the deeper field; but that wouldn't make Munich was any weaker.