For India, it's hard to change a majority-poor population into a majority middle-class population overnight, especially when the average Indian presidency lasts just 18 months and there is chronic legislative gridlock. Economics use a $3,000-$4,000 per-capita GDP benchmark at the point at which a country's economy starts to get the appearance of a more advanced world economy, and India is still far from that.
This is from the Cia factbook:
India: GDP - per capita: purchasing power parity - $2,200 (2000 est.)
China: GDP - per capita: purchasing power parity - $3,600 (2000 est.)
I suspect the margin will erode, and that it is already in the process of doing so.