Yes Mancini is a great manager........ So is Mourinho & so is Guardiola. If it's a comparison of all 3 you're after, Mancini has had to come from way behind where Mourinho & Guardiola did with their previous teams to achieve success with City so comparisons are unfair because it's not like for like.
The question you should consider is this, would Barca or Real suffer if Mancini were to become their manager tomorrow?........ I think not. Their infrastrucutures have been in place for decades, where as ours have only been in place over the last four years and it is only since last week that we can truly say for the first time that we have a first-class CEO & DOF to compliment our first-class manager & coaching team.
Give us until next summer for our management team to settle in & then let the comparisons begin. It will take us years to get to where Barca & Real are, but with the new academy on the way & a fresh footballing outlook, the comparisons for now should be between Barca & Real's success & our continued improvement on & off the field & City consistently narrowing the gap between them & us, these are the only comparisons we should concern ourselves with.