Wade Barrett, Alberto Del Rio, or Daniel Bryan. There's no other contest between these three. Wade Barrett for his immediate impact, Alberto Del Rio just because of how awesome he is, and Daniel Bryan for his matches.
This is a really tough call. Bryan's got a title belt, the momentum (three straight wins this week over the IC Champ in really excellent matches), the best in-ring talents of the three, and the best PPV run since his rehiring. Barrett's got the management push, the main event status, and the most creative angle. Del Rio has by far the best gimmick, the quickest rise (he debuted by "taking out" Rey Mysterio) and in my opinion, the best mic skills and most charisma of the three (slight edge over Barrett).
I honestly can't fault anyone for picking any three of these guys. I avoided picking Bryan mostly because I'm an ROH guy and I'm so familiar with him that he doesn't seem like a rookie. I opted against Barrett because I'm a wrestling fan, and of the three, he's put on the lowest quality in ring matches. My vote goes to Del Rio.
Wade Barrett. Del Rio is great too, and obviously has an all around advantage because of his excellent in ring ability, but Barrett is just TOO good of a heel. He's nailed how to act the WWE style. His presence is insanely commanding, he's like the Darth Vader of the WWE. Great mic skills, great look, great presence. Might not be the best in ring, but it's rare to get a good in ring big guy anyway. He ticks off every important checkbox.
Daniel Bryan isn't even in this discussion as far as I'm concerned, it's an arms race between Barrett and Del Rio. They have presence, he doesn't, and they have far better mic skills, charisma, gimmicks, looks, and what they've done in the WWE is bigger. I won't argue that Bryan is the best in ring worker in the WWE, or probably in the entire world, but all of that skill can't make up for what he doesn't have.