A nice combination of all three is the best way to ensure success and a long career.
Tours are also very important as they gauge one's true popularity and success.
No shade, but wasn't Rihanna having trouble filling arenas in the US, and Katy, even with five #1s, is only playing to 17,000 people a night (not saying that's bad, but it's kind of low when most arenas can hold, what 25-30,000? Correct me if I'm wrong, though.) If people are willing to actually come to your show, then you know the public's here for you.