Dhyan Chand - India's first international sporting hero. Hockey's decline in India makes his tale especially poignant (what is sport without a tinge of nostalgia?)
Gavaskar - Arguably, Indian Cricket's first world-class player. Gavaskar set the benchmark for excellence at a time when Indian cricket was content to merely compete.
P T Usha - Sporting achievements sprinkled with the tragic are pure gold dust. Here was an achievement that garnered more attention precisely because it failed (in terms of medals). But Usha inspired a hundred imitations and was a trendsetter, and not just because she was a woman.
V Anand - His achievements are phenomenal, and do not get due attention because chess as a sport is not that huge. The game is not ideal for TV viewing, which partly explains why Anand's exploits have been underrepresented in the media. In sheer sporting terms (achievement vis-a-vis international peers), Anand is undoubtedly one of the eminent (if not the) sportsperson of independent India.
Tendulkar - It is fashionable (almost hipsterish) to put him down. Yes, he probably stayed on too long, the Ferrari fracas was a blot on his image, etc. It would, nevertheless, be impossible to undermine his impact on Indian cricket and for raising the team's profile on the world stage. Tendulkar was India's first superstar of the media era, bigger than SRK, or any other actor. Unparalleled in terms of his pan-India marketability, and as Ram Guha said, very likely regarded with the same sense of awe and pride as a much-earlier generation thought of Gandhi and Nehru.
Honorable mentions: L. Paes - I stayed awake as a kid for his '96 Olympics bronze game, but fell asleep by the time the game commenced. Legend in the Davis Cup. In terms of showing passion on the field, Kohli could learn a few things from him.
Saina Nehwal - Garners media attention and people's respect for her sporting exploits rather than just being in the news for non-sporting reasons as someone else with a similar-worded name.
Dhoni - poster boy of the non-metro India. His cricketing legacy still has to be decided, but his impact on the game in India is unquestionable.