The young Brazilian has often found it difficult to hold a regular place in the City side.
But he was in fine form as he got the opener in a 2-0 win at Crystal Palace in the Premier League on Saturday.
"He [Jesus] will have a long career and with his mentality always he will have success. He is hungry, he will become an important striker around the world and we are lucky to have him," Guardiola told reporters.
"Gabriel was always good from the beginning. Unfortunately he had the two tough injuries. Last season it was tough for him, after the World Cup it was not easy, but he is strong.
"He is a number nine for Brazil. The club brought an incredible, young player for an incredible price. One of the best signings.
"To compete with Sergio [Aguero] is maybe the most difficult thing. Sergio is a legend, an outrageous player - amazing, but Gabriel is so calm.
"He is a competitor, he accepts the decision and every training session he fights like an animal, but he is so young and can improve."