He has too much creative control in his movies to actually ever have an iconic role, and his taste and choice of collaborators is very meh. Guys like WIll Smith and Stallone could make the creative control thing work, cause they were creative (Smith was a Songwriter, Stallone a Screenwriter). They had some taste.
Rock was a wrestler. And it shows in his career. He basically plays the same guy, with the same look, and the same performance, in every single movie. So lazy and unimaginative.