If only mainline passenger trains are considered (Since there are the only ones for which the number of train sis readily available) then the order is as follows:
1) Kanpur - Average of 197 departures everyday (Maximum number of departures is 201 trains on Tuesdays)
2) Vijayawada - Average of 162 departures everyday (Maximum number of departures is 166 trains on Tuesdays)
The remaining...
more... contenders are as follows:
Vadodara (BRC) - Average of 146 departures everyday (Maximum number of departures is 152 trains on Sundays)
Itarsi (ET) - Average of 130 departures everyday (Maximum number of departures is 133 trains on Thursdays)
This only includes regular, mainline passenger trains. (Specials and suburban traffic are not included)