It's a good question.
To answer the question of 'most famous' goal I think you need look at it from a nuetral perspective. So a none City fans looks up at the TV and sees a goal and immediately knows who scored and what where the circumstances.
Using this Criteria.
Aguero definitely number 1.
IMO Its a toss up for between Dzeko v Qpr and Vinny v Leicester fot spots 2 & 3.
I think there are also quite a few other goal before we get to Dickov.
From a City fan perspective Aguero and Dickov obviously 1 & 2.
Then it's tough. Law, Tueat, Tommy Hutch, Morley, Goater v Utd, Kennedy v Blackburn and then all the glory goals. Too many to mention.
For me personally the one that means the most is relatively famous with opposition fans is Yaya semi final v Utd. The day everything changed and dreams came true.
Most showed on tv city goals are probably.
Aguero
Ricky bloody Villa (I still scream chop him down at the screen when I see it)
Dennis Law