First of all, great thread, very interesting debate.
Man, I'll need to take some time to really reflect on this but I was brutally dissapointed by The Godfathers LP by Kool G Rap and Necro, I was expecting all sorts of epic from that record and it really came off as a Necro ft. G Rap project with little to no chemistry between the two artists and an inability of G Rap to shine on the beats which for the most part were very uninspired and poorly adapted to KGR.
I'll also say that I had huge expectations for Uncontrolled Substance by Rebel INS and Immobilarity by Raekwon and was extremely dissapointed by those 2, especially the later.
Of course every Nas and Snoop LP after Illmatic and Doggystyle have never been to my liking, but to call IWW the most dissapointing hiphop LP of all time is in my opinion overeaching. Personally, I've just stopped expecting any project worth listening to from Nas but always give his music a chance in the hopes that he'll come with some magic that will resonate with me, but he's simply no longer an artist that creates music that I find exciting. His music is just flat out boring to my ear.