Rey Mysterio, and by quite some distance. Look at the past year and tell me someone's been better. Last year he had a killer performance in the Rumble, and was basically the star. He was then the star of the Elimination Chamber, won the IC Title and meant it mean something with some great matches, including his awesome series with Jericho. Then had a good series with Ziggler and helped establish him as a serious midcarder with how he constructed his matches with Ziggler, had a great match with Morrison to drop the IC Title, came back and assisted in one of the best heel turns in recent memory (Batista is so much better as a heel than a face), and in between all of that managed to put awesome matches on on SmackDown! week in and week out.