I feel like many stake Nas's legacy and existence as an artist on that album. It is classic, iconic even, but it's like Nas stands in the shadow of that album in the eyes of many. It has grown in stature over time, but people act like it's the end all/be all of his career. That makes it overrated IMO. I think much of it being overrated has everything to do with it being underrated for as long as it was. When Nas became a star, it became the standard to put Illmatic on a pedestal even at the expense of dissing his other albums no matter how good they are.