The trick is to look beyond mainstream rap. Look for underground or indie hip-hop, and you'll find artistry, both in sampling, layering, rhyming, rhythm, and lyrics....the latter of which is often political, speaking about Black culture (i.e. diaspora, poverty, racism, violence, community, slavery, education, post-colonialism, etc, etc, etc.).
Unfortunately, I haven't extensively explored the rich culture of meaningful hip-hop, but I know it's there, and I've heard a lot that is beautiful. Just like
willravel said, rap (e.g. hip-hop) is essentially poetry to a beat, but with added rhythms, hits, and the occasional melody. Much of it prides itself on "borrowing" or appropriating popular culture as a way of either undermining it or reinventing it for its familiarity. But it all boils down to lyrics and rhythms.
There is a lot of bad rap out there (read: gangsta rap), but there is also a lot of bad rock.... really bad rock. I'm sure you know of a lot of bad electronic music out there, or at least genres that give your preferred genre a bad name by unfortunate association (read: techno, dance). Good hip-hop has this same challenge. As does good indie/alternative/progressive rock.
If you want to find some good hip-hop, try browsing the site
metacritic.com and find some of the highly rated indie hip-hop albums, and check them out. I'm not sure what's been released or reviewed lately, but some of the previous albums from other years I've checked out, and some of them are quite good. Another option would be to look for free .mp3 samples of indie artists online through various sites. I have no recommendations for any; I've been out of that loop for a while now.