The prolific City striker roared back to goalscoring form with a superb hat-trick in Saturday's comfortable 3-0 victory at Chelsea.
The treble took his Premier League tally since joining the club in 2011 to 99 in 146 appearances and his total in the competition this season to 21.
With leading scorer Harry Kane three ahead of him on 24, Aguero again has the Golden Boot - which he won last year with 26 goals - in his sights.
Pellegrini said: "He has scored an important amount of goals so he is fighting to be the top scorer in this year also.
"The way that he is playing, especially the last game, I am sure that it will be difficult for the other strikers to keep up with his performances."
Aguero will hope to reach his Premier League century against one of his favourite opponents, Newcastle, at St James' Park on Tuesday night.
The Argentinian has scored 10 times against the Magpies in league competition, including five in one game when the sides met at the Etihad Stadium last October.
Unfortunately for Aguero, that game proved his last for City for seven weeks as he picked up a hamstring injury on international duty
With heel trouble then hampering his comeback, it took the 27-year-old some time to get back into his stride.
The pattern of blistering form followed by injuries has become a familiar one for Aguero throughout his time at City and Pellegrini thinks that could be why he is continually overlooked for personal honours.
Only once in his five seasons in England has Aguero been nominated for the Professional Footballers' Association Player of the Year gong and he has never been voted into the players' team of the season.
Pellegrini said: "I don't vote so it's difficult for me to know why in four years he's never been (among) the best players.
"I don't know who chooses the best players, what the different reasons might be
In other seasons maybe people didn't vote for him because of the injuries but he's demonstrated in every game that he deserves to be in."
Pellegrini has stated in the past that he believes Aguero belongs in the same bracket of players as Lionel Messi and Cristiano Ronaldo and only injuries have prevented him attaining that status.
He said: "If he continues scoring three goals every game, he'd be very near them
The most important thing for him is to keep in the same way he's been doing this season and not to have important injuries for a long time.
"If he plays around 29/30 games this season, with just one injury which was with the national squad, I think that's important if he's going to be (rated with) the top players."
Source : PA
Source: PA