Peter Schmeichel, Eric Cantona and Roy Keane all make the list, along with current first-team players Ryan Giggs and Wayne Rooney.
Ferguson also argued that Paul Scholes could be regarded in the same bracket, and predicted that Cristiano Ronaldo would become world class.
However, the likes of David Beckham, Ruud van Nistelrooy and Bryan Robson were conspicuous by their absence.
"In my time I've been blessed with several world class players. Peter Schmeichel was certainly one, and Ryan Giggs for me, definitely," said Ferguson in the Manchester United Opus.
"Eric Cantona could have been even better, but for the parts of him you had to control.
"Wayne Rooney, that's four. Then there's Roy Keane, that's five.
"And I think Cristiano Ronaldo is going to be. He's playing in the hardest position, out wide, and never refuses to take the ball and attack players.
"And there's an argument for Paul Scholes, the cleverest midfield player we've ever had.
"To work with such people has been an absolute pleasure. It's fulfilled every aspiration."
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Is there something he knows we dont? How is Rooney considered in this bracket but not Ronaldo?
My guess is that Fergie looks at player from an all round perspective. Ronaldo, for all his skill, is still not a great team player, still very selfish (part of his attributes though), still doesnt track back often enough....
The fact that he names Rooney instantly is very suprising though- still not proved it in my eyes yet