Twenty years from now, both The Rock and Cena will be remembered for leading their generation of wrestlers primarily as a face. However, they both got to the top of the company as a heel.
The Rock won the Intercontinental Championship early on in his career; however, his one-dimensional face character got old quickly with the fans. He then turned heel and joined the Nation of Domination.
In this group, he actually acquired the name "The Rock." His time as a heel with the Nation of Domination, led directly to the top of the company and WWE Champion.
John Cena was not always the happy-go-lucky boy scout for the WWE that many believe he is now. He made his debut by taking Kurt Angle up on his open challenge and although he lost, his efforts in the match made him a fan favorite.
He then was part of the contest to name the first SmackDown Tag Team Champions, with Billy Kidman. After they lost, Cena turned on Kidman and ultimately became a heel. He then took on the rapper gimmick and was a heel. Cena rose to the top of the company as the "Doctor of Thuganomics."