Let's be honest, for Arsenal, I've seen him have good games against top sides about 2.. possibly 3x and about 12+ including games against us, where he's been somewhere between poor and invisible.
My basic problem with him is against the big teams, we're not "on top" for periods long or often enough for him to get on the ball, it would potentially be swapping invisible Mkhi out for basically the same issue. Where as.. if he went to City, with them being on top game to game regardless of opponent, you could see him reproducing his Real Madrid numbers.
Your only hope would be if Mourinho could squeeze more consistency out of his former player, though, judging by Mourinho's contract talks, flirting with other jobs, picking fights with the fans and 3 year job history, you wonder how long he'd be around to coach Ozil anyway.
Would love to get a direct player who can run at a defence and cause panic instead, honestly.