lyrically:
Eric B & Rakim: Paid in Full
Jay-Z: Reasonable Doubt
Nas: Illmatic
Biggie: Ready to Die
Slick Rick: The Great Adventures of Slick Rick
Boogie Down Productions: Criminal Minded
Eminem: (The Eminem Show, or Marshal Mathers; whichever one suits your taste)
hardcore:
Wu Tang Clan: Enter the 36 Chambers
Mobb Deep: Hell on Earth or the Infamous
MOP: Firing Squad
NWA: Straight Outta Compton
Dr. Dre: The Chronic
Alternative:
Mos Def- Black on Both Sides (or the Black Star album, that was excellent too)
Jurassic 5- Jurassic 5
A Tribe Called Quest- Midnight Mauraders
Gang Starr- Full Clip (yeah I know this is the greatest hits, sue me)
Common- Resurrection
Pete Rock & CL Smooth- PeteStrumentals
The Roots- (Pick one, )
I know there's a lot of down south music missing, but sorry, I rarely listen to it.