Population and Growth
The Times of India analyzes the relation between population and prosperity.
All the countries that Times' article cites that have nearly the same population density as India's, but are prosperous than India, have a very high degree of urbanization. This might be the only explaination for the difference in prosperity. Urbanization has a networking effect and can create tremendous propserity. Our own example of Mumbai illustrates this point clearly. Mumbai has highly dense population and it is also extremely prosperous.
Importantly, India's population is younger compared to many European countries and others. With the looming retirement of large number of 'boomers" in US, and European countries, it represents a great opportunity. This nations will be requiring lots of services and we have young working population. Already, growth in BPO, IT services etc. is reflecting this.