Silva has been key to City’s perfect start to their Premier League campaign, scoring two goals and creating two more and delivered a virtuoso performance in his side's 3-0 victory over Wigan at the Etihad Stadium on Saturday.
Speaking after the game, Mancini told the press: "Silva is a top, top player. I don't know why he didn't go to Barca or Real Madrid because he's Spanish but we are lucky because he's here.
"If he had gone to Barca two years ago everyone would say he's one of the best players in the world - and he is one of the best players in the world.
"He's different from [Lionel] Messi and Cristiano Ronaldo because they are strikers and score a lot of goals but I think he's the same as Xavi and [Andres] Iniesta."
Silva is one of many big money signings made since the club was taken over, and Mancini has admitted that it is hard for a number of his players who are forced to sit on the bench.
However, he feels that his rotation policy will help City in the run-in at the end of the season the season.
He said: "They may not be happy - that's impossible because every player wants to play always, but I'm the manager and I need to take this decision.
"Now we have a difficult match coming up [in the Champions League against Napoli], we play every three days and these players like Edin [Dzeko], [Aleksandar] Kolarov, [Stefan] Savic, [Samir] Nasri have played two games in four days and they need to recover.
"We have a long year and I need all the players to be available as much as possible and sometimes it's better that they rest.
"We have the first game in the Champions League for the club, it will be an exciting night but we need to have a focus and make sure we beat them."
Mancini will be taking the club into the Champion’s League for the first time, after his side gained automatic qualification with a third-place finish last season.