Its audible..listen to the chorus of Forgot About Dre.

He rhymes OVER the beat not TO the beat...there is a difference. JayZ rhymes in conjunction with his music. Its not about off beat/on beat...its about soul...listen and you'll here that Em's shit is off. On a track like Dead Wrong (where he actually came close to rhyming like he's connected to the the rhythm of the track) he was still off. Watch how he moves to his music....it tells alot (trememdous difference in comparison to them, you see the same differences that you see when watching a predominantly black crowd clapping their hands to the music than a predominantly white one.

and before y'all start, MC Serch actually has more innate rhythm..& is an example of a white boy who connects with "it".