OK...like many countries with big population...there is significant income inequality. 400 of the richest americans have more wealth than 150 million americans.
Getting back to your point ->
So how should that affect the fact that India is about to be the 3rd largest economy?
Per capita income is extremely low in India. But things are improving.
India's growth is mainly because of growth of service industry, manufacturing and modern agriculture techniques. The countries that you have mentioned have higher per capita income because of huge natural resources and less population.
Iraq -> Huge Oil reserves / Small population
Mongolia -> Huge mineral resources / tiny population
Or Mongolia for the 133rd position, depends upon who's list you look at.
Don't forget the huge income inequality.