That's interesting. Volcker was ridiculed tremendously at the time for his role in getting us off the gold-standard as well as his hard stance on inflation. I suspect that he is considered great now because inflation is considered a problem, but his actions caused more protesting than any other. Some would still criticize his influence on suspending gold convertability. I guess all that really matters is what the current issues are though.
I would say Volcker now. I would've said Greenspan if he hadn't ever cut rates below about 3%. The earlier part of Greenspans tenure I think he made some great decisions. Bernanke isn't really shining so far.