Dude I like a lot of Rihanna's songs but they are unabashedly POP drivel. Katy Perry probably has more conceptual/meaningful pop hits that Rihanna songs and she is undeniably centerline pop.
Only question I got is, whats up with eminem releasing 4 singles before his album drops over the course of 2 months. I mean this is the most epic push i have ever seen for an artist. 4 singles, 2 months, Sports/NFL affiliation, Video Game/Call Of Duty Affiliation, etc. I havent seen something of the like before, guess thats why interscope/aftermath stays on top.
They released 4 because only 2 of them got the full single treatment. Rap god is a promo single at best.
Berzerk = Full single treatment
Survival = Itunes and music video, but was never released/pushed to radio
Rap god = Only released to itunes, no video or radio push
Monsterc= Full single treatment
if you look at an itunes release as a fill single then relapse actually had 5 before the album (crack a bottle, we made you, 3 AM, old times sake, beautiful)...and perrys recent album had 4 (even tho the label only counts it as 2 because 2 songs were just released to itunes with no push similar to rap god)