It depends on what side of the hemisphere you're on.
Without doubt, Greece has had more influence on Western civilization. But, from mid-Asia eastward, you have to give it to China. They have always had the dominant influence on that side of the world.
Oh, a few. After having avoided reading these authors for years, I have finally picked up Orwell, Vonnegut, Hemingway, and a few others. So far, I am liking what I am reading. Some people I know turned me on to them. ;)
Oh my goodness, that's a tough one to answer. In all honesty, it depends on my mood at the time of writing. Sometimes I want (and never achieve) the eloquence and descriptive abilities of someone like Leo Tolstoy, and sometimes I want the simplicity yet effectiveness of someone like Cormac...