No one can really answer this fairly. Theres just about a hundered credible canidates including Flair, Bret/Owen Hart, Dean Malenko, Dory Funk Jr., Jumbo Tsuruta, Bob Backlund, Beniot, Jushin Liger, Great Sasuke, Ricky Steamboat, Lou Thesz etc etc.
You'd really have to review about a dozen hours of match footage for each guy. Some may call it too extreme to do that, but it isn't when a million people just blurt out Bret Hart without taking in other canidates at all as a possibility.
Chris Benoit no hesitation. He is the best techincally sound wrestler ever period. Iam not disrespecting the other guys but he never really changed his style unlike most of the others that adapted to what ever era they were in. Chris remained technical and that's why he is the greatest in my eyes and alot of people's.
Only ohter one I could think of would be Kurt,but I still say Chris over him. Olympic medals count but not in professional wrestling.