The Rock is pretty much another Arnold. Can't act but audience eat his unique on-screen charisma. But like I said in other threads, he will have Arnold's problem when he gets old and loses his physical attraction because like Arnold, Dwayne's on-screen charisma comes mostly from his physical attraction. People quickly lost interest in Arnold in the late 90's when his physical attraction dropped like a rock. This quick fading will happen on Dwayne one day.
This also speaks for why Stallone and Willis are having much longer acting career than Arnold, because they can act.