Not really, it isn't. They spent millions on established stars like Aguero, Silva and Yaya Toure. They spent a lot on young upcoming players such as Johnson and Balotelli too, their squad is superior to United's in almost every department(as individuals on paper), not to mention United were plagued by injuries at a couple of periods in the season. Vidic, their best defender barely played, when Kompany was absent for a few weeks, the effect of his absence was quite visible. Also, important players like Valencia and Nani missed large chunks of the season.
City have a superior squad, less injury worries and they have a lot of depth. Mancini has no excuse whatsoever in losing the league this season, he showed again what a huge choker he is, even the league titles he won with Inter, he only won them because calciopolli ensured there was virtually no competition for a few years. IMO he had his chance at City and they should definitely fire his underachieving arse.