North Korea has more man power than USA and they have a one milion men armed services which is like China.
man power is not a major factor in the modern warfare, for instance 3000-4000 British troops defeated 12000 Argentinians in Falkland (malvinas) Island conflict in early 80s.
Or Israelis defeated a united arab army (Syrians, Iraqis, Egyptians, Jordanian.... etc) in less than a week.
I doubt Russia can be any where near the top 5. The discipline of the red era is gone. Bribery is playing a major role in their armed forces and they dont have money to maintain their equipments.
but my personal ranking is: