For most people it is vision. Personally, it is vision for me as well. I drink in most of the world through my eyes. I should add that when people lose one sense, the other senses grow stronger and take on many duties of the lost sense. That is why elderly people with pets live longer.
Touch is life giving.
It comforts and soothes us. It connects us to the world and liveliness of life. If babies don't receive enough touch, they don't grow. I think that is true with adults as well. It is always wonderful to know that my books touch other people.