Ahead of the weekend's Manchester derby at Old Trafford, the Red Devils legend has questioned whether City will ever be up there with their neighbours in terms of worldwide support.
"There's no doubt, nobody can argue Manchester United is not the biggest club in the world. It is," said the great Dane.
"It's the club with the most fans.
"But Manchester City have been there or thereabouts so you can argue they are the bigger club in Manchester at the moment in terms of results.
"But in terms of popularity, they have got no chance of being anywhere near the biggest in the world."