I first began to pay close attention to hip hop in 1990. As a teacher in suburban Philadelphia, I wanted to understand the lives of my students, including the music to which they listened. I lay no claims to an encyclopaedic knowledge of the genre, or its performers, but I did realize very quickly that the lyrics and rhythms are intricate and sophisticated. I thought, this is, in its own way, poetry. And my students are memorizing impressive amounts of it.
Kelefa Sanneh, writing in The New Yorker, agrees. In "Word -- Jay-Z's 'Decoded' and the Language of Hip Hop, Sanneh takes a close look at the poetic form of hip hop (as opposed to its content), and reveals just how sophisticated the rhymes and beat can be. Rather than quoting from the article, I encourage all readers to check out the link for themselves. This underground-turned-mainstream form of expression has taken a bad rap (pun intended) over the years, based solely on perceived crudity and violent images in a few songs. This is comparable to judging all of classical music harshly after listening to the dissonances of John Cage. A deeper understanding is called for.
For insight into the creative process of hip hop, and for the cultural anger which drives some sub-genres, try viewing the movie 8 Mile, the autobiography of white rapper Eminem (shown below). Once you put together the raw sources of that anger, you begin to appreciate the power of the content, as well as the intricacy of the form.