The Argentine has been in devastating form for the Citizens of late, hitting 15 goals in all competitions, and Pellegrini is adamant that the 25-year-old is in a league of his own in England.
Speaking to reporters, the Chilean said: "I said last week that Messi and Cristiano Ronaldo he is the best. Both are not playing in the Premier League so he is [the best in England].
"He is a better player because he is older. He arrived in Spain when he was 18 or 19 years old. He was always a very important player, a top player, but this year he is trying to work a little bit more without the ball."
City, who have hit 34 goals in 12 league fixtures this season, welcome Swansea City to the Eithad this afternoon, one week after demolishing Tottenham Hotspur 6-0 at Eastlands.