How would you go about making such a ranking?

I wouldn't personally

Are you defining socialism to include the moderate fascist wing aka social democracy?

lmao

I'm not saying western countries are more likely, but what I am saying is just being in the close sphere of china isn't a magic socialism button, I think the fact that there are residual structures from the USSR that remain is a much better argument if you were to make one, but I also think third world countries would not be any less likely than Russia, some of the biggest communist parties and movements today exist in third world countries