The problem with hip hop nowdays is that good hip hop is still around, just nobody knows about it. Instead we are constantly bombarded with this Pop trash posing as hip hop such as anything done by Drake and the rest of Young Money, Soulja Boy, and Lil Wayne after Tha Carter 2.
It depends what kind of rap you like. If you are into underground, back pack rap, someone like Mos Def or the Roots stand out. The problem lies with commercial rap, which is all marketing, in many cases. A lot of it's success revolves around good production of club-bangers that make listeners rowdy, which really doesn't focus on lyrics as much as the back-pack style rappers. Also, there are TONS of repetitive themes in rap music, from artist to artist. When it comes to new rap, it's all been done before, just now it's done with better production and marketing. The rap genre has become a cash-cow, and it will be milked for here on out, so things will probably get worse before they get better.