The Argentine striker missed games against Manchester United, Bournemouth and Swansea City after being retrospectively charged for elbowing West Ham United's Winston Reid.
City managed to win all of their matches during Aguero's absence, but Gundogan is still pleased to have him back ahead of this weekend's Premier League clash against Swansea.
"Kun is very important for us. He has qualities that are very rare in the world, so we try to involve him in every game," Gundogan told City TV.
"We just want him to score for us in every game and to have him is a very good feeling. It gives us the safety that we are even more able to score. We are all happy he is back now after his three games."
Aguero scored nine goals in five appearances before his ban, including two hat-tricks.