Rock's got a reasonable range, but I can't remember a single role where I've ever seen him and not immediately thought 'the Rock', no matter what he was playing.
He's not just an actor, he's a movie star. So yeah, he's branded to be the main attraction and to carry his movies just like Schwarzenegger, Cruise, Ford, etc. before him.Then again, considering his origins and the over the top nature of most of his roles, it could just be a question of his branding.