Balotelli had everything - height, pace, power, skills and an ice cold ability to finish. By rights, he should've been one of the best in Europe.
However I could've written the same about Adebayor and plenty of other forwards. They have God-given abilities but as soon as they get to a certain level they seem to just stop wanting to be the best. In all honesty, the difference between the likes of Balotelli and Aguero/Tevez wasn't great but mentally the latter had something he'd never had.
My biggest fear with Balotelli when we let him go was Ferguson would take him on and make him into a Cantona type player for them. He had the ability but was just wasn't top class in the end as the rest of his career showed.