Cena is the guy for me because it comes down to 3 things
1. Credibility
Cena can be believed as a challenger to anyone. He has built his resume. He has earned his battle scars, cut hsiteeth, and fought for his place on every big stage and in any hostile environment. Everyone whether they love or hate him knows he can bring it, including the casualest of casuals. And again it goes back to who has Punk ever beat in his career clean? He went over Cena in a screwy fashion to get him to where heis, but he hasn't beaten A quality guys, and yes I'm saying Jericho isn't HHH, Taker, Michaels, Dave, Cena, or even Rey quality in terms of the win meaning something because he jobs too much to the wrong guys
2. Atmosphere
Make any excuse you want for Punk but he hasn't had that atmosphere he had last summer with any opponent but Cena. Not even Trips could get the same feel in their match. His mania match was quiet, people can make excuses but the fact is they didn't have the crowd like they should in that triple main event setting. Even now, his Jericho feud as some heat, but it isn't the same kind of heat that Jericho even had with Rey by simply demasking him. Cena gets a reaction, mixed, hate, love, whatever, it is always deafening in the building when he is put in a scenario and makes for great viewing on tv and even better in person.
3. He's earned it
Cena is the guy he is the one to bust his ass every night. He has been going harder since 05 than anyone on the roster not named Taker/HHH can even relate to. Cena is the guy working the most dates, filming movies, making the most wishes, and doing any interview with a smile on his face even when he logically feels like shit physically. He goes out there and he represents the company and himself well at all times. He is the utter professional. He is the guy who earned his way into being a draw, he earned his way into a relation. The belt was not handed to him to try and get him over like a Del Rio, a drug scandal like Punk, or to spite Brock like with Randy. He had to earn his shit and he never looked back after he finally got the reward. He became their best draw, he became a merch mover, he became the main attraction, and he became the big match guy who always out on a sow. Fuck the move or lack of wrestling bs, with the lights on bright he does his fucking job better than any full time wrestler on the roster and anyone who has ever seen him in person knows that. He is the ultimate showman. He is the guy of his generation. Because he is who he is, and the likelihood of a Rock, Austin, or Taker only having the one match left in them he has earned the right to be the first guy on the list to get that match over everyone else on the roster. It's real recognizing real, and with all due respect to every Punk fan, they even have to admit that Punk has not earned the right to possibly have Austin's one and only return match over Cena