I would assume a Ghost will have MUCH better chances of survival in an unarmed/unarmoured fight against a Zealot than a Marine. And obviously a higher chance of winning, which is still very low. For a human at peak physical condition to display such agility and reflexes as (for example) those shown by Zeratul in the StarCraft II opening cinematic would be practically impossible (even in a sci-fi fantasy universe

), of course Zeratul is pretty much the Protoss equivalent of Miyamoto Musashi so I wouldn't imagine an average Protoss warrior to be as deadly, but still quite formidable.