The issue hits newstands August 16, but if this year is anything like last year, name blocks of 100 will be posted to their blog right around that date as well. We'll be sure to duly cut and paste for the archives.
The Miz sounds like a fair choice for #1. Between June 2010 and May 2011 he had a run as United States Champion, coached a successful NXT rookie, won Money in the Bank, won the WWE Title, and went on to win the main event at Wrestlemania. The biggest black mark against him was the amount of trouble he had fighting Lawler.
Of the other likely WWE contenders, Cena was only Champion for about a month, Kane was only successful against Rey and a weakened Undertaker, and Sheamus' reign was largely helped by being in the right place at the right time during Nexus attacks.
Orton on the other hand had two successful reigns, and is worth considering. He presumably was hurt in the rankings by Miz defeating him on several prominent occasions. Edge's reigns were fairly dominant as well (not to mention he was a surviving victorious member of the Smackdown team at Bragging Rights, and his team was also victorious against the Nexus at Summerslam). Its harder to argue that his year was less spectacular than The Miz's.
On the TNA side, RVD was rather unstoppable as Champion, but had a weak year after his injury. Sting was out of action for too long. Jeff Hardy was having a good year before becoming Champion, and was the centerpiece of TNA during his reign. It looks like he was penalized by PWI for how badly he did in his match with Sting, and the time he took off afterwards.
Ah, but that leads to an even bigger problem. The lack of long term planning with the WWE in the past year+. How can the writers go into a WrestleMania with no plan for the soon to be former WWE Champion beyond WrestleMania?