Cube is a beast period but I don't count Kill At Will, its an EP not an album. He still probably has the best run of albums ever though.
However Common, Nas, Jay-Z & DMX are very close, each have 3. Common was on fire until Electric Circus (and then he started wrecking shop all over again starting with Be), Jay-Z was too until The Dynasty, Nas until Nastradamnus and DMX until The Great Depression.
Niggas are too in their feelings about this shit. I can explain why each album I chose is great, so I'm not worried.
I AM is a classic. It contains everything: storytelling, street records, mainstream joints, conscious thought-provoking materal, and great concepts. I could beat you across the head with it all day but you would have to be open minded, I see a lot of cats are too in their feelings about this shit though.