When Capone was boss they really only needed one racket, bootlegging. He grew it into an organization making up to $100 million a year from 1925-30, or more than a billion dollars annually in today's dollars.

He basically founded the Chicago mob and successfully ran, at that time, an organization that involved thousands if not tens of thousands of people. And he ran it so successfully that the only way the government could finally get him was by blindsiding him on tax evasion, which was something that had only been used sparsely at that time, and from what I've read the trial was pretty much a sham and he should not have been found guilty.

Overall I think he was pretty successful, although his management style was much more blunt and simple than the extremely cunning bosses who would follow him like Accardo and Humprhies.

In terms of body counts he must have one of the highest in terms of the number of hits he ordered.

And in terms of pure numbers of the organization it probably also reached its peak at that time.

On a personal level he wasn't very successful as he contracted syphilis and his life was essentially over by the time he was 40. But I imagine Al Capone never expected to live very long anyway. I remember some quote where someone asked him about the dangers, or overall negatives, of his job and he said, "That's true, but if I wasn't doing this what would I be doing? Shining shoes in Brooklyn."