It's Katy's first big tour. Most people do not come out with a 100M+ tour with just one big album.
It took Rihanna seven albums to do it. Taylor Swift two.
True.
I MEAN, Rihanna's been on several tours and is just now reaching the 100m mark.
When Rihanna releases her #1's 2-CD set, that will be the first and last Rihanna album I buy.
Her greatest hits album can easily be her biggest selling album ala Madonna's Immaculate Collection if she markets it right and the new single (s) added to it are amazing. She'd need a song & video better than WFL or Diamonds. Rihanna's videos (just like her performances) are always so uneventful and a letdown. Nothing memorable. She can do better.
DIL is at 9M tops. 4.9M in the US, under 2M in Europe, and bits and pieces elsewhere.
That's still pushing it. 5.1 million in North America, 2 million in Europe, 300,000 in Oceania, 600,000 in Asia, maybe like 400,000 in South America + Africa...
There's no doubt that Rihanna has the strongest arsenal of singles. I think she and Madonna are the only artists in my Top 50 most-played that I don't like.