In the West, I would guess either Marx or Dickens. Marx.
Ernest Hemingway... loved the detail he wrote in his books..
Confucious.. He wrote a lot in his day and is still churning out fortune cookies.
There are several writers who have impacted our culture. I think the most important ones are early Greek/Roman philosophers or Biblical authors or other classics.
I agree with your statements as well, however many writers have not written solely for fame or to be remembered for their specific writing style. People's writing styes are largely influenced by what time period they live in, other author's influence, etc. A lot of writers have only become famous until after their deaths (when their writings have been discovered).
I suppose this is true.
Some might suggest the Apostle Paul
Edgar Allen Poe!
Homer? A lot of stuff is drawn from him and his epics over the course of history.
So you mean prolific, not prominent.