Sanders, easily.
Haven't really heard any logical arguments for the others 2 yet. Green and Woodson were great, but Sanders took away half the field, who cares if he couldn't tackle, no one threw at him.
I'm trying to figure out how Green
didn't take away half of the field. He, too, tended to be put 1:1 on the opponent's best WR for the first 15 years of his career.

It's called selective memory, I believe. If you were to keep the players the same, but flip flop the personalities of Sanders and Green, all the Deion fanboys in this thread would be talking about Green as the most dominant corner instead of Deion.
Also, no one is talking about Deion's days with the Falcons and after he left the Cowboys. I was a huge fan of Deion when he played with Atlanta, and he had several games during his career with the team where he was the sterotypical matchhead and beaten like a drum. And when Sanders and Green played together on the same team in 2000, Green was clearly a better cb the Deion. If that's not logical proof that Green was a better cb than Sanders, I don't know what is.
What's funny is that Green actually spent more time during his career matched up against opponents' #1 receivers than Sanders. For the majority of Green's career, he was matched up against the other teams #1 wr and followed him around the field wherever he lined up. For much of Sanders career, he was assigned to cover the receiver on one particular side of the field, and more often than not that wr was the other team's #2 for obvious reasons.
The only convincing argument that can made for taking Deion over Green is that he's much more marketable.