Which of the five senses in humans is the most sensitive?
I suppose it's a matter of scientific opinion, but to me, the most logical choice of which of the five senses is the "most sensitive" would be touch. The body is covered with millions of nerve endings, on the entire exterior surface of the skin from head to toe. Even if some of the nerves are damaged, there are still many, many others to keep this sense intact.
Smell, vision, hearing and taste are all more localized, and more subject to damage. Smoking, burns, normal vision and hearing deterioration all take place over the course of a lifetime, while the sense of touch does so much more slowly.