A lot of China, at least, was closed to outsiders for investing.
As to market size to GDP, well, again, it's a closed economy. Lots of government controlled stuff. Communism and all that.
India is quite protectionist as well. Also remember that a lot of commerce in developing countries is done with multinationals - so all those large companies from the USA, UK etc are part emerging, in that they will grow their developing divisions as the developing economy grows.