No time to look at this in depth, and I'm not sure if this is the sort of thing you want, but just from a glance at the landforms:
Map A: Spain, China, and the Vikings each need ships to reach any other civ (Vikings on their own island, Spain and China separated by a peak at a one-tile chokepoint which is much closer to China than Spain.)
Map B: Sumeria and Ethiopia are each alone on an island. The Celts, on a landmass with two other civs at the ends of peninsulas, have huge back lines.
Map C: Rome, Japan, Mongolia, and HRE are each alone on a landmass. Aztecs have a two tile long, one tile wide diagonal choke point (due to peaks) that they have to get past to get off of their long, thin peninsula by land; if they can't, France has the rest of that enormous landmass to themselves.
Map A: Spain, China, and the Vikings each need ships to reach any other civ (Vikings on their own island, Spain and China separated by a peak at a one-tile chokepoint which is much closer to China than Spain.)
Map B: Sumeria and Ethiopia are each alone on an island. The Celts, on a landmass with two other civs at the ends of peninsulas, have huge back lines.
Map C: Rome, Japan, Mongolia, and HRE are each alone on a landmass. Aztecs have a two tile long, one tile wide diagonal choke point (due to peaks) that they have to get past to get off of their long, thin peninsula by land; if they can't, France has the rest of that enormous landmass to themselves.