Its also hard to find hardcore Eminem fans anymore, everyone who grew up listening to him in their teens became doubtful around the Encore period. (It can be for many reasons, one big one like Roz mentioned was because people were finally branching out into quality underground music but Eminem was enjoyable as a teen-mainly for his immaturity and the fact he was one of the few rappers you could find)
Your point of bringing up his Recovery sales also holds no legitimacy since Relapse sold 4.5 million copies and look how many people hated that album. Its more or less old time fans putting faith in their artist and purchasing his album based on his past performances regardless of how bad the product is.
Out of the 50+ people I seen that got the album they all pretty much agreed there was only 2-3 good songs although there was a few others they could possibly grow into later. I do the same myself, mainly in movies I'll keep watching films from the same actor/director even if their going downhill because they had classics back in the day and I'm bound to be suprised if my expectations keep going lower with each release. Its a dedicated, but unenthusiastic fanbase anymore.