Old topic that's been on many message boards, but....
I was watching RAW from 9/15/97, which featured a main event of Bret Hart & the British Bulldog vs. the Headbangers. I noticed that Bret Hart, while mostly a babyface for his career, was much better as a heel. Just the way he carries himself in the ring, his antics are much more suited to being a heel than a face. The way he kinda' slouches around, then motions to the crowd after a dirty move as if to say "oh, c'mon..WHAT?!!" In his early Hart Foundation days from 1985 to 1987, he was also pretty good at getting the crowd pissed off.
Others I thought of, off the top of my head:
-Kurt Angle
-Ric Flair
-Macho Man
Some guys were adept at playing both: like Eddie Guerrero, Hulk Hogan and (yup) Lex Luger. But some guys just shined more as heels.
I'm sure there are countless more "better as a heel" guys, so chime in with your picks.
Eddie was much better as a heel. He's similar to Bret in that aspect, and really shines in his '97 heel run in WCW, especially his stuff against Rey.
Others:
Benoit
The Rock
Jericho
As far as guys great at playing both, gotta go with Liger.
I disagree with Benoit. His character could slide between face and heel pretty easily. I never felt he was better as either.
My list:
Stan Hansen
Bam Bam Bigelow
Steve Williams
Bruiser Brody
Shawn Michaels
Scott Hall
Kevin Nash
Curt Hennig
Jeff Jarrett
HHH
Owen Hart
Jim Neidhart
Greg Valentine
Butch Reed
Terry Funk
Nikolai Volkoff
Ray Traylor
Scott Norton
Larry Zbyszko
Kane