OH shit, just saw this thread and read it all the way thru for a change (I was lookin for new shit to download). Guess i have to put my 2 cents in on the Tupac/Biggie thing: I gotta saw I'm a Biggie fan, but I think Tupac is alright (Anybody heard deadly combination w/ him, biggie and big L) I don't think he's the best, even if hes a legend. BUt as for the best rappers/groups (in my opinion)
Slick Rick
Outkast (all of their stuff is great, even though their older stuff (Stankonia and before) is the best
Digable Planets (REBIRTH OF SLICK!)
Tribe Called Quest (I can't believe nobody has said anything about them!)
The Roots
De La Soul
Beastie Boys
Talib Kweli, Mos Def
Jedi Mind Tricks
Big L (def one of the best ever: EBONICS)
DEAD PREZ (WTF is wrong with u guys?)
Anyway, it seems like everyone here thinks that once people get successful, they suck, and that all rap really has to be really deep to be good, but I think that even the most commercial shit can be good (even if it usually isnt) like some of those club bangaz are good songs u can listen to (ie Clipse)
Oh yeah, and Jay Z is good too (better than Nas) hahahaha

Edit: Does anybody know about any good Japanese rap? Like the beginning of Samurai Champloo (by the Nujabes)?