anymore, its just so saturated. Its hard to find hip hop with any substance these days. The beats are all the same and once one guy makes it he brings his whole crew with him, thus leading to other rappers in the mainstrem that weren't actually good enough to shine through and get discovered. There aren't many natural talents in the game right now. Unfortunately there's no room on the labels for them because people like the ying yang twins take their place. Anymore, most of its mindless.
Rap sold its soul for spinning rims and gold teeth. There is still good rap out there, you just can't listen to the radio to find it.
Is it going downhill? Possibly, once it became "acceptable" to the masses to listen to rap music then it lost some of its rebelliousness. A lot of people flock to things that are socially unacceptable, and once its no longer on that level then it loses some of its allure. But on the reverse side so much money was flowing into the hip hop labels/artists at some point it was bound to slow down.
You can't keep recycling hte same beats forever and hope nobody notices.