This question cannot be solved like this because every provides best of it which is different than others.
I have used tata, airtel, reliance and also vodafone. My opinion is that all provides best facilities which they can able to provide.
It depends on the customers, that which facility does he wants, and which company is best for that. Main factor is range problem. All networks are turning towards 3G now-a-days.
We must consider all the basic factors like range, roaming, calling rates, internet rates, messaging rates this will helpful to understand which company is best. Besides this schemes like caller tune, mms we have to consider.
" Life does not get better by chance, it gets better by change. "