I'd say a successful band is one that sticks together for 10 years or so and has one of those TLA or first-name awards or a top-40 hit or is actually played on the radio. I'm not into the music scene, but I noticed a discrepancy when checking out Pandora for Christmas tunes and finding an LDS station, but no specifically Catholic tunes.
Has there ever been a successful Catholic group or artist singing music you'd hear on your local Christian rock station? Not just an artist in any genre who happens to be Catholic or an artist who was successful, converted to Catholicism and started appealing to a niche crowd (i.e. John Michael Talbot), but an artist or group like the Newsboys or Toby Mac.
I think this is an objectively answerable question, there's a wiki page for Roman Catholic Musicians but it is lacking both John Michael Talbot and The Singing Nun.
I edited the question to say, since the Singing Nun since Sister Smile would be an example of a "success" in the music business at least, but I've already got her record and I don't need another.