As a Rams fan, I wouldn't have him as the best play caller. I would have him as the best head coach.
I think him getting the most out of his teams, taking two different QBs to a Super Bowl, winning one - puts him in a class with really only Reid, Shanahan and Harbaugh (for various reasons).
I think McVay has done more with less and been more impressive as a HC. But I have to admit that I think Shanahan and Reid are both better playcallers than McVay.