Well, successful like a priest who sells his religion to a mass of disadvantaged people whose lives suck and are desperate for an identity.
Oh, and I believe that some top video games are sold by them.
Most of the more popular artists from the hip hop/rock genre continously donate to charities and humanitarian organizations. One rapper (Nas also considered one of the greatest hip hop lyricists of all time) was nominated for a nobel prize.
There's a "Rock the Vote" movement going on right now where rock bands are doing free shows in order to get young people to vote.
Rap Artist and CEO of Def Jam Entertainment Jay Z has just recently done a humanitarian tour to bring awareness to troubles in Africa. Kanye West, another hip hop artist made awareness of the blood diamond situation in Sierra Leone public with his grammy award winning song "Diamonds are Forever"
Then on top of that, how often are people with disadvantaged lives able to find inspiration and strength through music? Probably a million of them ( a lot more but that's a modest number)