His goal record in the league between the ages of 17 and 20 was one every 165 minutes at Inter which is very respectable considering he spent a lot of time out wide. Then in his first two seasons in City his league record was one every 128 minutes which puts him in that bracket just below the likes of Aguero and Suárez, so I think you're being a tad unfair.
Ignoring the numbers, in his
teenage years he displayed a lot of great qualities for a forward. Composure, set pieces, striking, pace, power, first touch - all very impressive. He scored twice in a 3-3 draw against Roma when he was just 19 which proved crucial in the end seeing as Inter only won the league by 2 points, so he wasn't just a flat track bully by any means. I tend to agree that right now he's living off his reputation rather than his performances but this idea that he was never that good or that his reputation is largely down to his "controversial" personal life is absolute bollocks, in my opinion. He just hasn't developed well at all because seemingly he's not that arsed.