I will go by how over the gimmick got/has gotten and how well that person performs it;
1. Mr Perfect - There was a running joke that he was legitimately perfect. There was a point where people actually tried to LOOK for botches to rib him!
2. Undertaker/kane/Sting - Just the pure longetivity of the characters - legends who constantly try and reinvent themselves.
3. Goldust - Who would have thought Dustin Rhodes could pull off a creepy cross dresser? This character was HATED back in the day to his effeminate character and how amazing he was at being a heel. Equally great as a comedic face!
4.Chris Jericho (The guy is an actual rock star, which is exactly what Chris Jericho has been since his late WCW days - Ralphus was a roadie if anybody wasn't sure
5.Stone Cold Steve Austin - Had the whole audience behind him. The fan titled "catalyst" of the most successful point in wrestling history. A talented wrestler that didn't even need to display technical skills to get over because let's be honest - his character got him over. He was essentially a working class, blue collar guy that hated his rich, tyrannical boss.
Tie: Mr Mcmahon - His feuds with Austin were legendary and without Mr Mcmahon, i don't think Austin, or WWE, would have hit the heights it did. EVERYBODY in the late 90s were talking about their feud!!
HBK, HHH and mankind also narrowly missing out because nobody has reinvented themselves as much as these two. Two of the most hated and beloved grapplers in recent memory.
In no order;
Bully Ray - he does have everyone hating him right now and from stories years ago, he is supposedly to be a genuine bully.
CM Punk - He is hated (and smark loved) as a heel and loved as a face.
Cena - Love him or hate him, he has kids and women in the palm of his hand. He is a company guy that definitely lives upto his character - he goes FURTHER than any other person to keep the gimmick up too. He believes in respect and he constantly refers to himself and the fans as "we". His make a wish contributions definitely give the impression that he genuinely cares about the fans so not only is he "John Cena" the character in the ring, he pretty much LIVES in character outside the ring (especially when around fans). Not to mention, since everybody went part time (and edge and batista left), Cena carreid the WWE on his back until Punk was pushed.
Damien Sandow - His genius character is just amazing and he pulls it off well. He could be as stupid as a brick wall, but he definitely doesn't come across as someone "acting" intelligent and cultured, you genuinely think he is.
Del Rio - C'mon, the guy is over! He has cool mariachi band theme music and a goofy mexican side kick ! He's still smug, rich and vain outside the ring, but inside the guy is actually a pretty good grappler.