The discoveries and Darwin's argument for the theory of evolution by means of Natural Selection had an absolutely tremendous impact upon generations of people who viewed life from an entirely different perspective thereafter. Here is what one encyclopedia states,

Discoveries in evolutionary biology have made a significant impact not just within the traditional branches of biology, but also in other academic disciplines (e.g., anthropology and psychology) and on society at large.

Certainly, Social Darwinism has had a tremendous impact upon societies, at least until Great Society ideologies began to prevail so that the fittest would not survive.

I would say easily the telephone, especially if you consider the way smart phones with internet connectivity are revolutionizing the way people communicate and stay connected.  Your phone can be used to talk to anyone around the globe, text, pay your bills, do your work, or access you home computer.

I think it depends on how you define impact. The telephone (as mentioned above) has changed the everyday life of almost everyone. It has made global communication instantaneous, cheap and easy. However the theory of evolution changed the entire paradigm under which most humans live. The idea that we, humans, evolved over time, along with other species changed the way in we most people view the world. It changed the way science was studied. In addition, it is one the few scientific theories that is still hotly debated and contested. Anyone who has ever taught school in a highly Christian area knows that this is not a dead debate. For most people in the world the theory of evolution was huge step from a world where life and thought were based upon religious ideas, to a the mainly more secular world we live in today, based in large part upon science. While the telephone has changed our everyday life in such a short period of time, the theory of evolution continues to have a long impact in how we think, live and study.

There's no real comparison here.  The theory of evolution is not something that changes one's every day life.  Many people in the US get by without even believing it.  By contrast, the telephone changed essentially everyone's life.  You couldn't just ignore its impact the way you can ignore the intellectual impact of the theory of evolution.