Eminem - A solo artist or just featured?

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I have been listening to Eminem pretty much since his first albums came out. I loved pretty much all of his songs and my iPod is full of them. However, recently the only songs with Eminem rapping in are the ones that present him as a featured artist. It seems the he is slowly backing out of the music business and conforming to only one or two verses/chorus' in other artist's songs. My question is; is Eminem better as a solo artist or to you prefer when he is rapping as featured by another artist.