The Argentina international striker was at his best against Tottenham, scoring twice as City romped to a 6-0 home success, a result that lifted the 2011-12 champions to fourth in the table.
Aguero has scored 14 goals in his last 11 matches for City and the 25-year-old now holds a Premier League record.
For players who have scored at least 45 top-flight strikes in England, Aguero now has the best goals-to-minutes ratio, and his partnership with Alvaro Negredo – who netted a spectacular effort against Tottenham - has been excellent this season.
Pellegrini sang the praises of both players and feels that Negredo finds it "easy" playing with City's superstar forward.
"I've known Alvaro Negredo for eight years, that's why he's here, he's a perfect player for the Premier League," said Pellegrini.
"He likes the way the team plays, he's a very important player. The way the team plays is very comfortable for him.
"And he plays alongside 'Kun' Aguero, that's easy, because I think that 'Kun', Messi and Ronaldo are the three best players in the world."
Pellegrini added that he expected club captain Vincent Kompany would return to training on Monday.
Centre-back Kompany has been suffering from a groin injury and has not played for the club since October 5.
