The Argentine led the line for City as we got off to a winning start in pre-season against Club America.
Asked to assess Alvarez's performance, the boss was impressed by the 22-year-old's work ethic off the ball and quality on it.
Guardiola said: "Julian (Alvarez) was incredible, defensively he is quite similar like Gabriel (Jesus).
“Gabriel is probably the best, but he is close to him in aggression and how intuitive he is, he makes the runs and with the ball he’s absolutely brilliant.
"He can keep the ball and you can link with him without a problem.
“We have the feeling we signed a top-class young player for the next years to come, and we are delighted.
“The job that Marcelo Gallardo did at River Plate, we have the benefit, and hopefully he can grow up in an important league like Premier League.
"All the young lads did really well, and Stefan (Ortega Moreno), he did well.
"We are impressed with how good a keeper we have now – his composure, we are impressed.
"Kalvin, he already knows perfectly (the Premier League) - he needs time to understand what we want him to do and help him with his movements and shapes. We are very pleased."
The City boss also expressed his delight at De Bruyne's strong start to pre-season, believing the Belgian has picked up where he left off last season.
After recovering from injury last summer, the midfielder went on to grab 19 goals and 14 assists in all competitions.
And Guardiola believes that the 31-year-old's performance against Club America - in which he grabbed a brace - was an indication of the levels he is already operating at.
He said: "Last pre-season he arrived in bad conditions because of injuries.
"He took a long time to get his best condition but the start of this season was the opposite.
"We saw in sessions he’s sharp and strong and he continued with the same level as last season, it was his best season in terms of scoring goals and he’s started really well."