I think Jay-Z summed it up best on "Hard Knock Life":
"I gave you prophecy on my first joint, and you all lamed out
didn't really appreciate it till the second one came out"
When RD was released, it was viewed as an excellent album, but not necessarily an instant classic or hip-hop landmark.
But it got enough respect to put Jay-Z in the "best MC" conversation. XXL crowned Jay-Z the best MC alive in it's first issue (released in the summer of 1997, before Vol. 1 came out)
I think after Jay-Z blew up, people went back and gave it some more consideration, and it achieved the status it deserved all along.