Cristiano Ronaldo guided his national side Portugal to Euro 2016 triumph last Sunday (July 10).
Speaking to German newspaper Bild, Sir Alex said: "He has an incredible desire for football, Cristiano is looking forward to each workout. He always wants to be better, to win. He especially loves these big games.
"During my time at Manchester United, Cristiano was the player who developed the most. Through much hard work.
"He constantly worked on his shooting technique, with the right, left, his heading ability, his bounce.
"His performance improvement is incredible. And what is remarkable, today's football is so athletic, so fast.
"Usually top players can only play for about five or six years at the highest level, then it's over. Cristiano has been doing this for over 10 years. That makes him so exceptional.
"Every generation has its special footballer, Cristiano is currently."
Sir Alex had given Cristiano Ronaldo his big break in his career when he brought him to Manchester United from Sporting Lisbon in 2004.
The legendary manager insisted that Ronaldo's hunger for glory and his work rate sets him apart from his contemporaries of his generation.
On several previous occassions, Sir Alex have suggested that Cristiano Ronaldo is the best footballer among the current crop of players, even better than his fiercest on field rival Lionel Messi.