Infact a you raised a good question that cannot be answered easily.
I have been in USA for the last 4 years(working as a consultant) and prior to that worked in India for about 3 years(In all cities including B'lore).
Intially money is the driving force for any one who plans to work in USA. With the passing of years definitely the comforts, the life style and easy availability of various resources make the people to stick back to USA.
I am sure that the saving potential is more in USA than in India.Ofcourse u may feel the absence of native culture, but to my surprise younger generation in Indian cities are more westernized than the people who live here. They are more crazy about western foods than us here.
The lack of infrastructure, redtapism and the bureaucratic corruption etc make some people, afraid to come back to India. For example to start a new company it's easy in USA in terms of getting finance, approval etc than in India where u need to pay lot of money to move the things.Even for getting a driving license in India, one need to pay money (if is in urgency).Think of joining a kid in school. U need to pay in lakhs for admissions in India. But in USA education is free upto 12th standard(in govt schools).
Don't come to the conclusion that I am criticizing Indian people. Infact I decided to come back after 5 years as I feel more comfortable in Indai than anyother place in the world. But there needs to be a lot of improvement in our entire system to lure back all the people here.
I am leaving here to make my answer little ambiguous (will come back more on this) and allow other people to share their views on this lovely topic.