Ronaldo left Old Trafford for Real Madrid in a world-record deal earlier this summer.
Berbatov said: “Ronaldo was a fantastic player for us and I’m sure he will be very good for Real Madrid.
“But, for me, our biggest talent is and always was – even last season – Wayne Rooney.
“He is an incredible talent and will be one of the best players in Europe for many years to come.
“The scary thing with Wayne is he’s four or five years off his peak and, when you see the level he’s at now, that is almost impossible to get your head round.”
He added: “Wayne just loves to play football, it was what he was born to do and you can see that. He is not concerned about any of the glamour that goes with it.
“He amazes us on the training pitch almost every day and his hunger seems to get bigger with every game.
“His attitude and love for the game reminds me of a child who could spend all day in the park with nothing but a football.”
