Ice-T, who made the comparison, explained how he spoke to Dr Dre about the art of crafting music for his new documentary Something From Nothing: The Art of Rap.
"[Dre] said there's a difference between a rapper and a songwriter," Ice-T told MTV.
"Dre says, 'You've gotta write me a song. I don't need bars - I know you've got skills, but we need songs, so give me the hook first'.
"He says a lot of rappers get lost, but that's what Eminem does. They write these incredible songs, and that's basically what Dre likes to take to the marketplace."
The documentary follows Ice-T to Eminem's studio where the rapper explains his method for writing a new hit.
Speaking about the experience, Ice-T added: "It was like you were listening to a scientist."
Eminem recently confirmed that he has started work on his new solo album.
Watch the music video for Eminem and Rihanna's 'Love The Way You Lie' below: