Money Making aside, Cena has put on much better matches on a consistent basis in the WWE than Punk has.
In my opinion, Punk is still living off his Indy reputation when people refer to his inring ability. Punk's best match in the WWE was with Morrison, who is soon becoming the next Shawn Michaels in terms of inring ability. Morrison can make anyone look great.
Meanwhile, Cena has had great matches with every style of worker in the WWE, whether it be Michaels, Umaga, Orton, or Khali. Cena's consistency and proven ability to get the most out of any opponent can not be overlooked.