I've only seen Rondon get splattered by Bob Foster. I liked to watch Bobby Czyz, he was entertaining and had some skills but was not a "great" fighter. Graham and Benton were both very good and their styles are very appealing to me. Neither was great. Better than Czyz, though.
I would say of that list, only Graham could be considered a great fighter. All four were very good fighters.
Graham and Benton. Benton was brilliant. He was a great fighter IMO. Benton was every bit as great as Graham
All of them fall short, for me. Graham the closest one to attaining that lofty status, which as others have said gets bandied about way too liberally. It's all fine margins, though - he gets that disputed decision against Gavilan when the title was on the line, and this discussion might look very different today.