I'm pretty sure that MLK and Desmond Tutu would be quite notable even if their minority status wasn't a factor. I'm not familiar enough with jazz music to be able to say much about Louis Armstrong one way or the other, but Scott Joplin certainly qualifies as successful (The Entertainer is possibly his most popular piece, but he wrote plenty more of course). And what about sportspeople like Pelé (one of the greatest soccer players of all time)?