Not really, I've heard plenty of better freestylers. In a shorter mano-e-mano battle, Eminem would probably win, but when it comes to fully-formed freestyles, Canibus is in a different league to Em. He's an overhyped, overrated pop-star now, he's never had the vocabulary to compete with Bis, or countless other less famous MC's.
Plus, that stuff in 8 Mile isn't anything special. He's just putting rhyming couplets together.