There is no doubt that Cena is the biggest superstar at the moment and the face of this era. He is also the hardest decision to make on this list.
Is he past his prime? Has Cena given the WWE all he has?
Instinctively, the answer is yes. He has been the face of the WWE for six years, amassed 12 world championships and paved his legacy through "hustle, loyalty and respect."
We are now at the crossroads of Cena's career. His character has stalled due to the lack of change. Cena has played the same character for six years. Normally, this wouldn't that bad.
However, Cena's character is built on overcoming odds. After six years, the mentality of fans is that he never loses. Most of the time, that is true.
That's why, under the current Cena character, his best years are behind him. He probably has four to six more years as the face of the company, and if he doesn't tweak his character, the fans will become further disillusioned.
If Cena changes his character, he will have far more to give the WWE. Mostly because he hasn't been heel in eight years.
Verdict: Past his best years in his current character.
His Prime: The two-to-three-year period between 2006-2008.