If you're trying to start a rap collection and you're new to it, you should sample some of the classics(Anything by NWA, Eazy-E, & Dr. Dre), then listen to a lot of other artists. Wu-Tang Clan has a style of their own that you will either like or not like. They speak in complex metaphors that sometimes make sense to few, you just have to appreciate the music. If I could only buy (or DL) 11 complete rap albums, they'd be:
"NWA Legacy Volume 1" - NWA (2-disc)
"The Chronic" - Dr. Dre
"Chronic 2001" - Dr. Dre
"Eternal E" - Eazy E
"Doggystyle" - Snoop Doggy Dogg
"Watermelon, Chicken, & Gritz" - Nappy Roots
"The Marshall Mathers LP" - Eminem
"The Eminem Show" - Eminem
"Wu-Tang Forever" - Wu-Tang Clan (2-disc)
"Enter the 36 Chambers: Wu-Tang" - Wu-Tang Clan
"Undaground Legend" - Lil Flip
There are probably a few I'm forgetting I'm sure, but those came to mind first. Also, many artists dont have albums that are listenable for all the way (or close to all the way) through the CD. Those ones I listed are definitely SOLID.
If you're just downloading songs and want a taste of the above, get these songs:
NWA: "Straight Outta Compton". "Always Into Somethin", "Fuck The Police", "100 Miles & Runnin"
Dr. Dre: "Nuthin But a 'G' Thang" (the best rap song ever), "Let Me Ride", "Keep Their Heads Ringin", "Put It On Me", "Still D.R.E.", "Forgot About Dre", "What's the Difference", "Big Egos"
(and I could go on for another half hour typing his good songs...)
Wu-Tang Clan: "Triumph", "C.R.E.A.M.", "Tearz", "Iron Flag", "Reunited", "Method Man", "Do You Really"
Eazy-E: "Boyz N The Hood", "Just Tah Let U Know", "Real Muthaphukkin G'z", "Nobody Move", "Automobile"
Nappy Roots: "Awnaw", "Po Folks", "Blowin Trees", "Lifes A Bitch"
Lil Flip: "The Way We Ball", "Forget the Fame", "We Aint Scared"
Eminem: "Cleanin Out My Closet", "Till I Collapse", "Stan", "Who Knew", "Kill You", "Criminal", "Bitch Please 2"
Snoop: "Whats My Name", "The Shiznit", "Gin & Juice"
from there, download these:
"This Tha City" - Pastor Troy
"Victory" - Do or Die
"Tormented" - Tech N9ne
"Rosa Parks" - Outkast
"Bring the Pain" - Method Man
"Ante Up" - M.O.P.
do a search for "rap list" and you might turn up a giant list I typed for a thread about gym songs