If we're talking Greatest Rock Singer it has to be someone like Mercury, Plant, McCartney, someone big and iconic. For me I think of the old Wembley Stadium sold out, Freddie prancing around like a nutter kicking so much ass it's untrue and Brian May ripping it up like nobody's business. Steven Tyler and Axel Rose are also great and that Stadium-rock tradition.
If we're talking most galvanising battle-cries that the common man probably hasn't even heard of then these are two of my personal favourites.
Voice perhaps only bettered by this guy: