Maradona has spoken out on the 23-year-old forward, who is enjoying a successful spell at the Etihad Stadium with 16 goals already scored following his £38million switch from Spanish outfit Atletico Madrid last summer.
And, he feels that Aguero 'made a mistake' in joining City and it would be in his best interests if he returned to Spain in the future to further his career with Real Madrid.
The former Independiente hitman has claimed he would never play for a team starting with the letter 'R', in reference to Racing and Real Madrid, but Maradona feels he should forget the rivalry and make the move.
Maradona accepts that City would be reluctant to sell Aguero, but he thinks Real president Florentino Perez could entice them with a suitable cash offer.
Maradona told Radio La Red in Argentina: "Kun has to play for Real Madrid. If he signed for them, it would be his big break. Even though he is flying at City, the best thing would have been to sign for Madrid. He made a mistake."
He added: "Now, as he is doing so well, it will be difficult to get him from City. They will want to keep him because [Roberto] Mancini has him very much in his plans.
"However, if Madrid want someone, they get them. Florentino has no limits. It's a question of convincing City, but not with money because they have plenty of that.
"If Kun was playing for Madrid they would close in further on Barcelona. We would be talking about Cristiano Ronaldo scoring 60 and more goals, because Kun would move the entire defence."