Ganguly is widely credited with giving players chance at the highest level and Dhoni was one of them, which eventually led him to scoring a marathon 148 against Pakistan in Vizag in 2005. Rajput stated Dhoni is also of the same mould as far as giving young players chance and confidence is concerned.
Ganguly was aggressive ( possibly getting ill treatment in his earlier days from the then team management prompted him to change his attitude), visibly aggressive and transformed his aggression into the team. As a result, the boys under him started to believe in themselves more and got a never say die attitude. The biggest gain was India’s performance abroad. India was always a tiger at home but with changed attitude, the team started believing in it’s calibre even on the grounds of Australia, England and South Africa. As a result, Ganguly remains the most successful Indian captain outside Asia by a wide margin than everybody else (believe it or not, India won it’s first test series even in Zimbabwe under Sourav). This changed attitude has helped the captains who came after Sourav in a big way.
When Sourav was handed over the captaincy, India was passing through one of it’s most dark times after the match fixing scandal in which the previous captain and a few other players were implicated. His biggest achievement was bringing the credibility of Indian cricket back within a year. Nobody raised a finger to the Indian cricket team since then.