The German driver has won nine of fifteen races on his way to sealing the drivers' championship title for a second successive year but Briatore ranks him as the third best in the world.
"Vettel is definitely good," Briatore told Corriere dello Sport.
"But he has won because he has been the best to manage his phenomenal [Red Bull] machine. He is not the best.
The 24-year-old became the youngest driver to ever win the championship last season.
The current Formula One season continues in Korea at the Korean International circuit in Yeongam this weekend.