Like you say, it’s generally the big games, in which we do well, where the atmosphere is best and there’s been far, far more of them in the 22 years at the Etihad than in the 22 years that preceded them at Maine Road.
In those 22 years at Maine Road there were two FA Cup Quarter Finals (1981 and 1988) one League Cup semi final (1981) three Derby wins (1981, 1989 and 2002) about four end of season promotion ‘deciders’ (1985, 1989, 1999 and 2000) assuming the Bournemouth, Wigan and Birmingham games count as such (and one of those ended in disappointment).
No European games at Maine Road in that period.
During that period we beat Liverpool and Arsenal three times each at Maine Road.
Overall that’s easily less than a game a season.
Of course there were other games where for various reasons the atmosphere was great: Villa in 1986, Palace in 1987, Leeds in 1992 (twice), Villa in 1995, Norwich in 2002 and our last game at Maine Road immediately spring to mind - but big games where we won, which made for an incredible atmosphere, given the timescale involved, were not actually that frequent.
Compare that to the big games we’ve won at the Etihad, where the atmosphere has couldn’t be anything less than incredible, then it’s simply no contest. If I was going to guess, it’s at least three a season in average. Even before the takeover we had as many Derby wins in five years at COMS as we did in the previous 22 at Maine Road. Since we’ve moved to our current home we’ve beaten United 11 times there!
People, understandably, sometimes look at the past through very rose tinted spectacles, because it represents their youth and a time when they had less troubles and responsibility, but the reality is that there have been far more amazing atmospheres at our current home than our previous one, as much as Maine Road was the main reason I fell in love with City (alongside Dennis Tueart!).