Ronald Reagan was one of the greatest in my opinion.
How on earth has GEORGE WILL not yet appeared on this list?
I love his patience. He sits with perfect poker face while the hapless lib rhetorically meanders about like a fly buzzing by the spiders web. One begins to think that he is accepting the logic. When the hole is deeply enough dug, he calmly decimates every last scrap of the fallacious tedium and constructs a steel framed work of logical beauty to replace it.
How often have you seen his unworthy opponents just wither before him?
Since you said all-time I would have to say Alexander Hamilton. Contemporarily, without a doubt Roanld Reagan he killed RFK in a debate once.