If this is about the THRILLER of Hip-Hop, then the answer should be RUN-DMC's 'Raising Hell'.
The same way that Thriller changed the sound of r&b and pop, Raising Hell changed the look and sound of rap. Fun fact, not only was Michael Jackson the first Black artist played on MTV, RUN-DMC was the first rap group played on the channel. The Kings from Queens were the group who got rap played in Utah & Oregon while little Billy was watching music videos.
As far as longevity, "My Adidas", "It's Tricky", & "You Be Illin'" still crank, and you "Walk This Way" is still being played over the PA system at your favorite sporting event.
Honorable mentions:
Eric B. & Rakim - "Paid In Full"
De La Soul - "3 Feet High and Rising"
Public Enemy - "It Takes a Nation of Millions to Hold Us Back"
Ice Cube - "Amerikkka's Most Wanted"
Nas - "Illmatic"