Tough to say man... Eminem is a battle rapper 95% of the names mentioned are not. The only 3 who could be viable candidates are Nas, G Rap and Andre 3000. You would need a battle rapper to beat Em. Niggas don't like Eminem but you have to realize he really is at heart a battle rapper, that's why he works so hard on the technical aspect and like MOST battle rappers he's not entirely the best at penning songs so it's understandable that some of yall can't find tracks yall really like on repeat. That's where Dr.Dre comes into play tho.
BTW Jay-Z is NOT seeing Eminem lyrically, he couldn't even beat NaS and Eminem DID murder him on his own shit. Battle rappers will smoke 99% of the game, you wanna beat Eminem ? Find a battle MC. You not gonna find rappers that can outbar Eminem and LOLOL @ niggas sayin Crooked and Royce, maaaannn them niggas will tell you they can't out rap Marshall LOLOLOLOLOL.