City currently sit top of the Premier League after 20 games, leading their rivals by three points, and their manager feels the competition in Manchester this season is extremely intense.
“It’s difficult to say your neighbours play the best football,” Mancini told reporters.
“It’s hard. But I think until now we’ve played the best football in the Premier League.
“In every city where there are two teams, the rivalry is very intense. Rome, Milan, everywhere it’s very strong.”
Mancini has likened the situation in Manchester to that in Milan when Inter were in the shadows of their prestigious rivals AC Milan.
However, under the Italian and then under Jose Mourinho the trend was broken and it’s now Inter who are the top dogs in the city - although the Rossoneri won Serie A again last season.
The 47-year-old is hopeful of bringing the same sort of success to City as they look to enjoy similar feats to those United have achieved during the last two decades.
“[AC] Milan were at the top for many years, winning the Champions League and the championship,” said Mancini.
“For Inter this was very, very difficult because Milan won everything.
“Here we have the same situation. It’s clear Manchester City don’t have the same history [of winning as many trophies as United].
“But when you arrive and start to build a new team, a strong team, and afterwards it becomes as strong as the other team, for me it’s the same.
“In one or two years we can catch up. United have had this winning mentality for 25 years. If we win the title or another cup then we can catch up.”