To touch on another issue here, someone mentioned sampling. What's great about sampling, from the perspective of people like Dre is that it provides you with an instant hit.
Any musician will tell you that the hardest thing to do is write a hook. It's easy to write a song that will impress your fellow musician with your knowledge of chords, modes, counterpoints and what not, provided you have a musical background, but writing songs to impress an average Joe who doesn't know a musical staff from a wizard's staff is tough. You need a hook, something to catch your listeners attention. It could be a chorus, an intro, a riff, it could even be just a couple of notes, but you need a hook.
Just about every hip-hop song to achieve mainstream or crossover success has been sampled. And hey, it makes sense. If you're Eminem, why waste time and energy composing and recording your own beats when there's all the Didos and Aerosmiths of this world to take them from? Sure, you have to credit them and pay them, but that's small change compared to the money you'll make.
Case in point. I won't name the song in question, but I'll point out that it was probably the biggest mainstream hip-hop hit of the 90s. How many of you knew that BOTH of its hooks were sampled?
Now, I'm sure someone's gonna point out that the song is good, sampled or not, but I'll also say that the version of the song everyone knows is a remix. The original version had a completely different backing beat and was not a hit by any stretch. Oh, and wouldn't you know it, even that different beat is sampled.
So, I mean, aside from lyrics, what's original here? And if the lyrics are what this is all about, then why make music? Just publish a book of poetry.