I worked in the telecommunications industry for many years. In my humble opinion, nothing beats fiber optics as the material for a telephone transmission line. You can put massive amounts of information on that beam of light, and it’s far more durable and flexible than copper.
I realize that fiber can’t be used for everything. Around the house you’ll have copper or coaxial for most of your needs and they will suffice. However, fiber is the medium of the 21st century, in my opinion, for communications needs that we face.
Personally, I don’t think this medium has really been tapped. There are miles and miles of dark (unlit) fiber sitting underground waiting to be used. This is largely due massive infrastructure spending in telecommunications companies that eventually went bust, but I believe that we will need all of this fiber again one day.