Ethan Carter III - Not sure if improved was the right word, since he really hadn't been given a chance before
Roman Reigns - He's getting better, but I think he's mostly just gotten over rather than greatly improved
Goldust/Stardust - Goldust is the same guy he's been since he came back. If Stardust was a choice on his own, he might get my vote.
Seth Rollins - He would be an excellent choice for this. He was pretty much just the flippy guy in The Shield, but has moved up to one of the top heels in the company, with much better mic work than I though he was capable of.
Dean Ambrose - I don't know if he's improved as much as he's just on his own now. Very similar to Reigns in that respect.
Ryback - Turning back the clock to 2012 isn't improving.
Erick Rowan - He's never impressed me in the ring, but I'll hold off judgement for a while until I see more of his solo stuff.
Dolph Ziggler - Same guy he's been, just with another push that I hope won't be aborted like the rest.
Nikki Bella - She has gotten a lot better. The Bella feud was pretty bad, but I don't think either one could've pulled it off as well as they did even a year ago
Eric Young - No idea, but my guess is no.
Tyler Breeze - As much as I loved the character, when he debuted, I really didn't think it had staying power. I was so wrong. Breeze is one of the best things going today, and would finish in second or third for me.
Winner: Tyson Kidd: He's always been a top notch wrestler, but his new douchebag character is excellent and he plays it to perfection. NXT has easily been the best wrestling show this year and Kidd could very well be its MVP. Plus, bonus points for making something good come out of Total Divas.