Jake Roberts get my vote here, it was hard but all in all I liked him a lot as a heel, he has a phenomenal in ring presence that you didn't see with anyone else and the fact that he actually wrestled is what edged it for me.
Also, the fact that people are surprised he beat JBL just surprises me? Do people not remember the lack luster career Bradshaw in a whole had? He debuted as Justin Hawk Bradshaw, then went on to join up with Ron Simmons as the Acolytes in the ministry, which went on to be a long run as the APA that spent more time in the back playing poker with jobbers that actually wrestling in tag team matches. He had a run as a face in the singles division which was poor and almost unwatchable in my opinion. Then he suddenly came in a John "Bradshaw" Layfield and won the belt and albeit had a hell of a run on top, but after that run as champ he sort of drifted into the mix of main eventers.
Then you have Jake Roberts, a guy who could cut a promo better than most and the guy had an in ring presence like no one else. Sure, he didn't hold any titles, but back then it wasn't important. Jake Roberts in a whole was more memorable that JBL ever was, and that's just a fact. If anything I would have been disgusted to see JBL beat someone like Jake Roberts in a greatest heel tournament.
This is just me, and don't get me wrong I loved the JBL character but not enough to constitute a vote for him over Jake Roberts, they were even in the same league and that is that friends.