Which is the credit card with best rewards to fee ratio?

SBI Cashback Credit Card

Hdfc infinia is my go to card

Amex travel platinum - convert the points to mariott points (redemption for anything else is average). Bonus is if you do the conversion during their bonus transfer, also you get Amex offers (spend x and get y - usually a 3-5% return). Happy to give you a referral if you need.