I like rap and like talking about it. The new Big Boi is very good. Better than Speakerboxxx, which I also like. I don't think I've ever heard melancholy done better in rap than
Unhappy from that album. Second the ATLiens recommendation, throw in Aquemini too.
And of course Illmatic, which really should serve as a template for all rap records. Excellent production, no obnoxious skits, absolutely no filler and flawless delivery on every track.
Enough can never be said about Public Enemy. I'm not an expert on the history of rap, but they may have been the first really sonically interesting group. It was all pretty basic before them.
Other favorites, somewhat in order, and off the top of my head:
Liquid Swords -- GZA
Madvillainy -- Madvillain (Madlib and MF Doom)
The Unseen -- Quasimoto (Madlib)
The Blueprint -- Jay-Z
Enter the Wu-Tang
2001 -- Dr. Dre
Slim Shady LP and Marshall Mathers LP -- Eminem
Champion Sound -- Jaylib (Madlib and J Dilla)
Only Built 4 Cuban Linx, the original and "sequel" (though quite different) -- Raekwon
Supreme Clientele -- Ghostface
The Chronic, Doggystyle and other various Dr. Dre stuff from the early 90s
The Pretty Toney Album and giraffescale -- Ghostface
Purple Haze -- Cam'ron
Ridin' Dirty -- UGK
Dr. No's Oxperiment -- Oh No (Madlib's brother)
Also, it's worth checking out as much J Dilla as you can. Maybe start with Donuts? That would probably be somewhere on that list.
Edit: My favorite
J Dilla track.
Not really rap or hip-hop, though the influence is there and heavy, but I love the new Flying Lotus, Cosmogramma.