For me, the best wrestler doesn't neccisarily have to be have the best pure wrestling ability. There is a ton of things to consider, and actual wrestling, for better or for worse, is only one aspect of it. That's why you can't choose Shelton Benjamin in the "best wrestler" category.
I think that for someone to be classified as the world's best wrester, first and foremost, they have to wrestle for a major promotion, namely WWE or TNA. I know that all of the hardcore independant fans won't agree with that statement at all, but it's the truth. Take your example of Bryan Danielson. True, he's a fantastic wrestler, but he can't land a job in the best promotion. Why? He's clearly a better wrestler than John Cena, but Cena is a huge star in WWE. The difference is that Cena has tremendous charisma, mic skills, storytelling ability and a great presence.
Then you have guys like Chris Benoit, Dean Malenko, William Regal and Finlay. All are obviously very talented wresters and in-ring technicians, but aside from Benoit winning the WHC once, none of them progressed much past the mid-cards. Again, while they all worked or are working in WWE, they lacked, or lack, that X-Factor that sets someone like John Cena or Triple H apart.
After working in a top promotion, you have to be able to talk on the mic. That is just so important. Honestly, a lack of mic skills are the only thing holding Shelton Benjamin back right now. MVP can talk, Shelton can't so MVP gets the push.
Wrestling ability is probably next, but it has to be the right kind of wrestling skills. Sure, Dean Malenko is a god to hardcore wrestling fans, but to the average fan, he's boring. A star wrestler has to have an entertaining move-set that can keep the crowd involved over the course of an entire match. Plus, they have to have a dynamic and exciting finisher. Look at Cody Rhodes. The DDT? How original...
Also, a great wrestler has to be able to wrestle different styles and work with people who don't always compliment the way they like to compete. A main event guy should be able to work a standard match, a technical match, a hardcore match, work fast, go slow if the situation calls for it, basically whatever is needed.
Calculating all of the above up, I have three picks for a "best" wrestler:
1) Shawn Michaels: To me, Shawn is the complete package. He can do everything in the ring, he can pull of a classic with anybody, he can tell a story, he can just do it all.
2) Edge: Edge is a close second behind HBK. He's exciting, he's unpredictable, the fans just despise him, he's got a terrific move-set and he's proven many times over that he's a great champion and can work any type of match and make it memorable. Very few people are better at putting a feud together than Edge.
3) Kurt Angle: The obvious pick. He's not working with WWE, which is why I didn't rank him higher, but he's a great heel, has better wrestling ability than anyone on the planet and is excellent on the mic. I can't wait until he comes back to WWE.