Referring to EOs only now:
I have visited most of the "old countries", and so far, Romania seems to be the most pious, also much more than Greece. That goes for countries as a whole, and I must say I still haven't been to Georgia (hopefully will do that soon, though), of which I have heard many good things.
As for EOs being in a minority/missionary situation, I guess the US is really doing quite well, but so are Albania, France, the Czechoslovak church...
As for OOs, I must say that the only ones I really know more or less well(in the old country and the diaspora) are the Copts. Their personal piety is impressive. But their reluctance to proselytize amongst Muslims is disappointing. I mean, I know it is dangerous, but if every Copt was ready to participate and risk his life, I am sure that there would be a Christian majority in Egypt again very soon.