The club's all-time leading scorer returned to City's starting line-up for the trip to South Wales after being benched for the Champions League clash with Lyon, which ended in a 2-1 defeat for Guardiola's side.
Aguero opened the scoring at Cardiff City Stadium after 32 minutes, connecting with Bernardo Silva's cross and sending a first-time shot into the net, and Guardiola was pleased with his performance.
"Hopefully he doesn't finish, decide to retire or go to another place," City boss Guardiola said of Aguero, who extended his contract until 2021 on Friday.
"He played good, he created chances and, yeah, it was a good performance.
"He had a little injury, he came back quite good."
Aguero's opener was quickly followed by goals from Bernardo Silva and Ilkay Gundogan, who both caused havoc in the Cardiff defence with their incisive runs and constant endeavour.
Guardiola, who saw Riyad Mahrez score his first two goals for the club to wrap up an emphatic win in the second half, described his side's performance as better than the one that earned them a 3-0 win over Fulham in their previous league outing.
"I think we played better than the Fulham game," said Guardiola. "We were more dynamic after a bad result in midweek.
"It is not easy, but after one or two goals, it was immediately easy. We created a good game and good chances.
"Today was excellent."
The Spaniard gave his players a message of support after they bounced back from defeat against Lyon to win in such style, saying poor results would not change his opinion of his title-winning team.
"It's the same players," he said. "Nothing is going to change my opinion of them.
"They know the worse the result, the closer I am to them.
"They deserve all my respect. They made me happy for two seasons, and that's why I will always be there with them."