There are so many great writers living and dead, and who have written in so many different genres, that I would not hazard a qualitative comparison to choose an overall favourite. There are so many that I like that I can (almost ) do an A-to-Z list quite easily: Austen, Bradbury, Clarke, Dickson, Eco, Forester, Graves, Hemingway, Ibsen, Jack, King, Lewis, Maguire, Nabokov, Orwell, Peters, Quinnell, Rothfuss, Shakespeare, Tolkien, Updike, Vonnegut, Wilde, X (hmm, X is a problem), Yeats, Zafon. And of course, standing alone in the zombie naturist genre there is Stuart.
Then there are those best not mentioned . . . Atwood springs to mind.
Books are nutrition for the mind. You are what you eat.