Please shutup with 'one good year'. Just because he sold a record breaking amount one year, doesn't mean that he doesn't have constant success.
He spawned #1 hits for 5 consecutive albums becoming one of the only 5 artists to do so, became the 3rd artist in history to go #1 in 3 decades, and even in the R&B charts he broke the record for longest time between first and last #1 for an artist.
The top-selling album of '04 in US sold 8 million, and the top-selling album of '08 in US sold 2 million copies. So it's dumb as **** to always come for it being a decline, when it also had to with a huge shift in the album market overall. Even if he had the top-selling album of 2008, it still would've sold 4x less. Do your research. You continue to look unaware.