Shawn Michaels was the best overall IMO. I'm talking the look, mic skills and pure wrestling ability. HHH would be a very close second.
My opinions on the best in specific areas:
body: Scott Steier or HHH
mic skills: The Rock
techical wrestling: Bret Hart
high flying: Rod Van Dam with an honerable metion the Superfly Jimmy Snuka
gimmick: Stone Cold