No doubt the TATA's.
They have not only done business but also have helped in building the nation.
They have given us
1. IISc Indian Institute of Science
2. TIFR Tata Institute of Fundamental Research
3. BARC
4. TISc Tata Institute of Social Sciences
And these are not only money making institutes, they are pillars of nation's knowledge.
And of course, their electricity is cheaper than Reliance (and even BEST and MSEB)