Perhaps no artist’s decline in popularity has been as scrutinized over the past half-decade than 50 Cent’s. After building up a feverish buzz through extraordinary work on the mixtape circuit (don’t get it twisted—conferences or not, Maybach Music Group has no claim to the mixtape game like G-Unit does), 50 Cent released the highest-selling Hip Hop debut of all time: Get Rich or Die Tryin’. 50 ca…