Butler was a pretty hardcore gangster as a middle-schooler, who figured out his calling and got rich/famous as a result of mistakes he made and time spent behind bars. So I'm sure his story is interesting enough for a movie (and obviously a good movie depends on a lot more than that).
Hopefully it's done better than Get Rich or Die Tryin' (and in that movie, the main character's acting wasn't one of the problems, Fifty was actually solid).