Ferguson's Premier League champions were comprehensively outplayed in May by a rampant Barcelona, who had United chasing shadows for the majority of their 3-1 Champions League final victory at Wembley Stadium.
Guardiola said the dominance of his all-conquering Catalans should not detract from Ferguson's trophy-laden reign at United.
"I cannot be compared with Ferguson," Guardiola told reporters ahead of Barcelona's friendly against Hajduk Split in Croatia on Saturday.
"The fact Manchester United lost a Champions League match doesn't mean I am a better coach than he is.
"I still have a lot to do just to attempt to be compared to him. The kind of prestige he has isn't lost for losing a match in the Champions League," added the Spaniard.
"When a person is working for more than 25 years and winning and winning and winning so many times, if there is one person I think is number one it is Alex Ferguson."
United overhauled Liverpool as the most successful English club in May when they won their 19th league title - Ferguson's 12th Premier League crown since joining the club in 1986.
