He doesn't have the Elvis effect for many, many reasons.
Number one, he's never released a phenomenal, game changing album in the vein of Nas, Rakim & Eric B, Wu-Tang Clan/Rakweon, Outkast, 2 Pac or even Kanye West and now might as well add Kendric Lamar. He's released good albums (Infinite, Marshall Mathers, The Eminem Show and Encore) that sold well, but he's never released something that's never been a must listen to per se, in the same vein as an Illmatic, Paid in Full, All Eyez on Me, Graduation or Late Registration. Try putting any album he's released up against Only Built 4 Cuban Linux or 36th Chambers, or his latest album against To Pimp A Butterfly. It's night and day.
Also, while I agree a 100 percent with him that album sales mean jack and shyt as long as the musics good, but again, most critical acclaimed hip-hop albums, most artistic mediums had some form or another of corporate backing. Just because something is corporate doesn't make it bad, shyt there were plenty of "corporate" backed rock artist that made it work, Nirvana, Sonic Youth, NIN, SOAD etc.