Redknapp wrote in The Sun: "City have gone for off-the-peg, top-of-the-range players. That makes life difficult for you as a manager because of the egos, even if it can bring relatively quicker glory.
"From a management point of view, there is something extra pleasing from seeing players shine that you have brought up through the youth team.
"Beckham, Scholes, Giggs, Butt, the Neville brothers. I doubt the like of that will EVER happen again.
"I was fortunate to see that happen for me at West Ham with the likes of Joe Cole, Frank Lampard, Rio Ferdinand, Michael Carrick, Glen Johnson and Jermain Defoe.
"They were nurtured by our Academy and for a time they made up half the England team.
"This kind of player is deserving of kissing the badge. We're seeing more coming through now at old Trafford with Tom Cleverley and Danny Welbeck.
"So when it comes to records, City's unbeaten run is good - but I'm afraid it just doesn't compare to Ferguson's at Manchester United."