I have to be honest in saying that I don't think people give Cena enough credit. The majority of the wrestling he does he does good, and I personally think its more WWE pushing him to do only the selection of moves he does in each match. If you look at his "I quit" match with JBL it shows he is very capable, and certainly he can get it done on the microphone better than many people.
I think Cena's good run was when he was fighting JBL all those years ago. Since then he hasn't really evolved as a wrestler, ie few new moves and hasn't really polished his current offence, nor has his program (I mean seriously aside from a few months here and there he's just been going for the World Title).
To me Cena is all about power, there's no technical skill in his work (especially when you compare him to most of the people he's feuded with, especially second generation wrestlers who are naturally more gifted then a first generation wrestler). So much of his offence is about emphasising how strong he is, finesse is perfectly acceptable too.
My chief complaint about him is that he can't sell, people like Orton HBK and HHH will get a 'second wind' and hit the moves they need to hit to win a match even after taking a ton of punishment, but they'll still show that an area that's been worked over is hurting. When Cena fought HBK at Mania several years ago HBK worked over his right leg for like 15minutes, not only did Cena not sell it when he got his second wind he wasn't selling it after the match and that's not a one of thing with him.
His mic work these days is pretty meh in my opinion considering his idea of being intense is just yelling. Whereas people like Edge, HHH, Orton they change their tone of voice for different effects (eg ice cold to show contempt or dropping to low and quiet to be threatening) as well as yell.
Sheltons one of my favorite wrestlers(and I think J.R. calling him possibly the best pure athlete may not be far off), and I think he does still have what it takes to be as good of a champion on ECW as Matt Hardy was, but I think WWE really dropped the ball with him when he was in his absolute prime with charlie haas.
Shelton is by far and away the best pure athlete in the WWE, I have yet to see anyone who can do half the things he can (Evan and Kofi are probably as close as you'll get). And the other thing is that he's not just able to do the freaking spots he's famous for he's also an extremely solid mat wrestler.
They certainly dropped the ball, but then Shelton has stuffed up in the past too (been in the doghouse for having the wrong attitude) so it's not all management's fault.
Which is probably for the better. There is no doubt in my mind he needed to get the jamaican gimmick when he started(as he has came a long way since he started in both promos and wrestling). However I also though that Kofi had what it took to be the next rock or cena, and if they manage to get both Randy over as heel while getting Kofi over to the main event scene right now I think he has that opportunity.
Kofi's gimmick definitely needs changing if he's going to become a main-eventer. The Jamaican one was fun and all but it's a mid-carder's gimmick, not a main-eventer.
I'm still not sure if Kofi's gonna be the next Rock, cause the Rock was probably a one of a kind guy (not to mention one of those pure naturals as a Third Generation wrestler), I think the next 'big' guy in the company who isn't an established main-eventer is Morrison.
But they do need to push Randy now to make up for wrecking yet another of his title runs. The problem for Randy is that he's at a stage where he can't go back to "The Legend Killer" gimmick cause he's no longer the brash young up-and-comer.
"The Viper" just doesn't seem like a good gimmick or one that really works. I'd advocate something like one of HHH's old heel gimmicks, cause I think that'd fit best.
I myself am one of the few who like the idea of the Guest hosts, its just too bad they are handling it in the wrong way. Certainly hosts who have nothing to do with wrestling or even remotely watch it doesn't help. But I think the problem is that people watch wrestling to get into the storylines and forget about what else is going on. Then once someone from the real world comes in it sort of ruins what they had going. However thats just my personal opinion.
Gotta say I want the idea to end. It does interrupt the flow of storylines, instead of a steady flowing storyline it's just a show a week with less connection to others then there was in the past. Plus too many of the guest hosts are basically faces, I think we've only had like 1 heel guest host in the whole run of the concept (Dusty did set up John but he was basically a face for the whole show).