If I can use my favourite artist as an example, and agree with gooddelta, it all goes around in circles.
Celine couldn't stop selling albums in the 90's. The Colour Of My Love, Falling Into, Let's Talk About Love, These Are Special Times and All The Way just sold and sold and sold. Even on her big comeback in 2002, A New Day Has Come sold bucketloads before she went to Vegas. One Heart sold moderately whilst she was there and even the insipid baby inspired Miracle album charted respectably. Now though on her much hyped comeback the lead single "Taking Chances" is doing nothing for her and it seems the album is falling out of the top 10 after just a week too.
So I guess everyone has their time to sell loads, swings and roundabouts really.