As has been posted, large numbers don't always equal victory. Sometimes they do, as some mentioned the zulu victory over the british, they surprised a small british force with a large Zulu force, but then the british came back with another invasion force that was better matched in size and still the same technological advantages and made quick work for the remaining forces.
In economics, China has a large, poor economy of many lower income people who are no longer dirt poor, just lower middle class poor workers, and a lot more wealthy people of course. Their billion + population and 2nd largest economy in the world demonstrates its large size, but not yet any impressive per-capita achievements like the economy of Japan or that of South Korea.
In Battle who's victory agbainst overwhelmingly larger forces is more notable than the Persian vs Greek Wars when Xerxes overwhelmed the greeks eventually at Thermopylae but then the Greeks destroyed the Persians in the Battles of Salamis, Plataea, and Mycale.
A tiny greek island nation of syracuse held off the romans with the help of his improved siege weapons.
India, like China, is a poor but growing country with over a billion people. They do not live there like most people in developed European or American states.