I guess its only perceived that United have lesser fans than City in Manchester is because they do have more fans globally than City... A lot more actually...
It is always easy for non-United fans or anti-United groups or better still, City fans to make such a simplistic statement but if anyone care to take a little time to think with logic, the truth and fact of the matter will come to light very fast...
Perhaps it it true that 80% or more of City's fans are from Manchester alone... and maybe only 20% of United's fans are in Manchester... But we have to remember we are dealing in percentage and not straight numbers to numbers...
The truth is, every week United have a sell out crowd to their 76,000 stadium while City struggle to fill their 48,000 City of Manchester Stadium... So where does this whole 76 thousand people come from? Outside Manchester? Every week? Cos a lot of United's fans who goes to OT are also season ticket holders...
So, like I said... Perhaps it is true 80 or maybe 90 percent of City's fans are from Manchester... And United, if we take into consideration the millions of fans around the world they have in different continents, it is only logical that they have more fans around the world than Manchester itself... But that little percentage of 20% or maybe lesser than 10%, could still be a lot more than City's precious little of 90%...
So i guess it is true that United are more famous globally... And it is also sensible to say they have more fans worldwide compared to locally in England... But we should not be mistaken that those little percentage doesn't necessary mean they have lesser supporters in Manchester... it could just means they have more fans around the world thats all...
http://www.epltalk.com/who-are-the-best-supported-clubs-in-the-premier-league/3471