I would say Shogun's a little stronger than Silva on the ground, but not so much to impose his will and make an easy pass. Power in striking/skill in clinch - tie. Speed on his feat, movement and hand speed - Silva is way ahead.
Also I think GSP would edge every MW with the exception of Silva and perhaps Vitor (TBD
?), I think Vitor's could be in his prime, like much better than what he showed against Martin.. I can't get past the sheer power and superiority he displayed against Ace and Lawler. Vitor is a guy that can shoot up or drop way down on my rankings win or loss to Silva.
A Silva, Shields and Okami actually improved IMO when they fought at 185, I see GSP doing the same.
@ MW GSP would be much faster than the fighters, he'd throw as much power as an Okami, but faster, still have reach advantage over most, even more superior cardio, better wrestling, more slick and stronger on the ground, maybe he might even have gas and comfort to let his hands loose in the stand-up department (as long as he doesn't see the other opponents striking as a threat) --- enough to beat the rest of MW his typical 5-round fashion.