He's too far to be come one of the best. Too many players ahead of him... plenty.
He's not bad but not a potential power. I could be wrong but I've watched him pretty too much to make my decision.
In this case age does count, imo. Especially since he's Italian. So many of the negative aspects in his game, the immaturity in certain situations most of all (not only his temper, but also some decisions to needlessly dribble when he has the ball), can be forgiven due to his age and can be fixed in the future.
We know how Italians, especially the big clubs, rarely give chances to such youngsters and when it happened, almost always those youngsters proved to be great players. Some might say that a foreign coach is the one who's playing Balotelli, but lets not forget that Balotelli started playing under Mancini, not under Mourinho. Both Mancini and Mourinho were doing what the Italians almost never do...they played, even important matches, with a 17,18 and now 19 year old in the team.
The fact is that at the age when 99.9999999% of the Italians his age can't even get a place for a relegation struggling team, Balotelli already played 56 matches for Inter, scored 18 and assisted 9 goals, with goals and assists in Serie A, Coppa Italia and CL. And on many of these 56 matches he came as a sub. Plus, with players like Milito and Eto'o, or previously Zlatan, he wasn't getting regular football, and yet he's scoring a lot and assisting. Oh, and he's also scoring against big clubs. He already scored 3 goals against Juve, 3 against Roma...also 3 against Genoa, 1 against Fiorentina.
The huge talent is there for everyone to see it. His problem is that he's aware of his talent so many times he's trying to overdue things, not to mention the attitude of his.