It seems to me that generally speaking, rap doesn't age well. The one exception being the late 80s early 90s era, but in my mind, that's different because that was the era that basically started rap as we know it. Artists from that era were actually pioneers. But since then, there aren't that many rap artists from 10+ years ago that are looked back at fondly (unless of course, they're still active and popular today). There may be the exception here or there, but it happens much less often in rap than in other genres. With rock music, entire subgenres from decades past are listened to and loved just as much as the fans that existed during that era. And to be honest, I think the reason is that rap songs often have less things about them that really grab you as something you'd want to hold on to for years.
PS: If anything could make JohnnyNemesis start posting again, it would be this thread.