Aguero, the £38million summer buy from Atletico Madrid, came off the bench to score twice and set up another goal in a sensational debut appearance in the 4-0 win over Swansea on Monday.
Dzeko said: "It's amazing for a new player to come on for the last 30 minutes and score two goals. I am very happy for him, but I am also happy for City in getting a player like him - he can only help us in the future."
He added: "And he is not even 100% fit yet. In the next games he can only get better and better. He scored twice when not fit, so we can't wait to see what he is like at 100%.
"Every good player is welcome to our team as we want to win titles."
With Carlos Tevez looking increasingly likely to stay at City - beyond one more transfer deadline day at least - and Mario Balotelli to return if side issues are addressed, Dzeko is under pressure for his place.
The 25-year-old struggled for goals last season after his arrival from Wolfsburg in January but has been lifted by a fine strike in last week's Community Shield and the opener against Swansea.
Dzeko added: "The beginnings have always been slow for me, and that was the case at City, but this year I feel fit and I feel very good. I feel much better than last season.
"For every player it is important to be fit and have a good pre-season behind him. This summer I have done everything with the team and that makes you feel better."
"I want to improve in every game, but I have started the season well. I try to do my best in every game to help the team."
Source: PA
Source: PA