Chris's reputation is tarnished for the pop/Top 40 crowd, as evidenced by DWMU & Y3X especially. Both of these were pretty big radio hits that I heard all the time, yet they sold poorly compared to their airplay on the pop format.
He, Drake & Future are the kings of urban/rhythmic radio (Future the feature king, kinda like T-Pain was). Chris has built up a huge loyal fanbase on that format, and people always underestimate his power when it comes to that.
He's made all the right moves with his past few singles and videos, from Fine China to Love More to Loyal. These 3 songs alone are better than all of Fortune, which is a weak album from him, hence the underperforming. FAME was miles better.
