At the moment I think Randy Orton is the best wrestler on the current roster, and I actually think we probably haven't seen the best of him since he has always taken a back seat to John Cena. He is technically very talented, good looking and decent with a microphone, he plays a heel character very well but can also be quite likable.
As for who was the best, I guess it depends on the era and what you are basing it on. You cant argue with Shawn Michaels being one of the best of his generation, and although he couldn't wrestle his way out a paper bag, Hulk Hogan changed the entire face of the industry and he deserves some credit for that.
On technical skills guys like Kurt Angle, Dean Malenko and Chris Benoit have to be near the top of the list. For showmanship you have guys like The Rock, Stone Cold Steve Austin and to some extent Triple H who were all at the top of the card for a long time due to their charisma as well as their wrestling talent.
Then of course there are guys like The Undertaker and Ric Flair who are in leagues all of their own.