I would say the most OVER right now has to be Cena. Yeah I know a lot of people don't like him (I'm not certain why). He seems to only want to work and I've heard a lot about how he helps "the boys" backstage try and get over. Wasn't he also the one who went off on Vince about how shitty the shows have been?
As for the others.. I think Daniel Bryan could be up there, and maybe have the title for a while. He certainly gets a good crowd reaction, and he seems to take his wrestling seriously.
Ryback could be huge if they would develop him a bit more. People keep saying he's a Goldberg clone. I seriously don't think that is his doing. I'd blame that one on Vince or whoever gave him the gimmick. I personally liked his look better in OVW. They should let him grow his hair back (unless he can't) and get him some more experience on the mic, instead of just saying three words. They certainly could use this Shield angle to build a good feud for him.
As for Sheamus.. I'm not a fan. Maybe it's just this Big Show feud, but I find him extremely boring. Randy Orton is good but he too seems really dull. Alberto Del Rio... really I shouldn't even comment. This guy is WAY over rated. His gimmick puts me to sleep... "I am da reeeeal apex predatorrrrrrrr". Sure... CM Punk is good as the champ... but even his situation is getting stale. He needs someone new to feud with. Or at least a much bigger angle, giving how long he's been the champ. To have him drop it to Cena or The Rock will just blow. Kane.. eh.. Kane is mid-card. Don't get me wrong, I am a big fan of Kane but I just don't see him being a top guy anymore. And as far as The Undertaker.. I seriously think WM will be his last match. He's just too beat up.
One thing I wish they would really do is have LESS belts. Have the WWE Heavy Weight Champion, Tag Team and Intercontinental. Then have the guys have to fight for #1 contender spots. Cut back on the PPV's and have title matches then. If a #1 contender loses at a PPV, then he goes back to the bottom of the list. At least it would solve a few problems. It would increase the prestige of the belts, and it would move characters along and give them a purpose. They are fighting for #1 contender. It would also rotate wrestlers around with each other. In stead of having back to back PPV's with the same matches, it would always be something new. Case in point, who the hell is really excited to see Big Show vs Sheamus for the 3rd straight PPV? Not me...
If you wanted to talk the Tag division, I would seriously get Sin Cara to learn English so he stops botching moves. I think 99% of his problems are miscommunication. Team him up with Rey like they have been and you have a solid tag team. Keep the Uso's together, maybe put Tyson Kid with someone and you could end up with a solid tag division. But please for the love of god, stop slapping wrestlers together and putting "Team" in front of their names.
Anyway that's my thoughts. Sorry I got a bit off topic. My mind wanders a lot.