Ron Cook's performance isn't that of a star, but of a fine ensemble player who is still part of the world around him. The comedy is there, but restrained, never really breaking the frame. He looms large, but not larger than life.
But there's another way of looking at the play and the character, not more valid, but equally valid, I think. This is to see the role as a vehicle for a star, a Burbage who will eat up the stage; this calls for a Richard who wrenches the conceptual frame containing him so out of shape that we know it cannot hold him. Even in his defeat he is thrillingly alive in a way those around him are not. I'm not talking here of psychological depth, though. I'm talking of dramatic possibilities - Richard has no depth, he is all actor, all surface, personifying something of the demonic power of the stage itself.
This is the Richard that Kevin Spacey brilliantly rendered last night. He blew everyone else off the stage, such that sturdy performances were made to seem wooden. I say this not in any spirit of criticism of those performances. The (im)balance felt right. Our Hollywood star wasn't upstaging anyone. The sense of ensemble playing was still there, and Sam Mendes in his direction played scrupulous attention to the full world of the play - rightly showing that that world is never truly alive other than when Richard is bustling within it.