Originally Posted by josephscott 
Help me out: name some contemporary Hip-Hop that is as exciting and as relevant as Boogie Down Prod., Eric B and Rakim, etc, were back in the day?
I mean, there's a lot of good Rap - Ghostface, DOOM, Ghostface and DOOM together, etc. (lol) - but Hip-Hop pretty much died with the live Hip-Hop DJ (so much so that it's more accurate to call them 'turntablists' now).
I'm not complaining, though. Late-80s sampling ('It takes a nation...', 'Paul's Boutique', etc.) was amazing and the beats The Neptunes did on the last Clipse album were also pretty out there.
Styles die and are reborn as something new (Blues to Rock 'n' Roll to Psychedelia to Metal to Punk to No-Wave...).
C'est la vie dans la musique...
Like Tommy Lee Jones said in Men In Black, Elvis is not dead, he just went home, and I strongly believe "alternative" hip hop is very much in the same state. I can name you quite a few hip hop musicians that fits your "exciting" and "relevant" criteria. They may not be in the same category as Public Enemy and the like in terms of genre classification, but they're all born from the same tree. Here are just a few:
Flying Lotus
Jay Electronica
Janel Jneiro
Luke Spicer
Blu (& Exile)
J Dilla (even though he's dead, but then so are Biggie and 2Pac)
Black Milk
Common
Murs
9th Wonder
Madlib
Q-Tip
Shad
To name but a few that I know. Unfortunately, their sounds aren't mainstream enough and you'd probably never hear them without the internet.