Former Australia skipper Smith retained his position at the top of the ICC Test Player Rankings after the Ashes with Kohli sitting behind him on the second spot.
"These are questions not to be answered. How does it matter? It's about performance. Virat is the best in the world at the moment. So that's what makes us happy," Ganguly told reporters on the sidelines of Tata Steel Kolkata 25K launch. Ganguly is the face of the event.
Asked about Smith, he said: "His records speak for itself... 26 Test hundreds which is a phenomenal record."
Ganguly was also asked about his ambitions of becoming the next India coach.
"Let one coach finish, then we will think about the other coach," said the 47-year old with a smile on his face.
"In any case I am already a coach. I look after the Delhi Capitals in the IPL. In my first season last year, they did well. They went to the semifinals from being last for last seven years so it's been good."
On MS Dhoni's future, Ganguly said: "I don't know what the selectors think, what Virat thinks. They are the important persons, let them make the decision."
Ganguly also said India are the favourites to win the T20 and Test series at home against South Africa.
The first T20 got washed out in Dharamsala and the second rubber is on September 18 in Mohali. India will also play three Tests against the Proteas.
"India are favourites. India at home is a dangerous team. They are very hard to beat and that's been the case for years," Ganguly said.