Donald T. William's article "Writers Cramped," argues, among other things, that the writing of good Christian literature requires a liturgical sensibility. With only one possible exception, Williams argues, all great modern Christian literature has been written by non-evangelicals. The only possible exception he cites is Walter Wangerin, a Lutheran. And even here, he points out, you have someone from a liturgical tradition.
I don't think, however, that Wangerin is even in the same class as Flannery O'Connor or Graham Greene, which leaves us with no protestants at all except C. S. Lewis, who was also from another liturgical tradition: Anglicanism.
Williams seems concerned primarily with fiction, of course, although he includes writers noted at least as much for their nonfiction prose: Chesterton and Lewis being primary among them. Although some of Chesterton's fiction could lay a claim to greatness (particularly The Man Who Was Thursday), I'm not sure Lewis's fiction could quite equal the others on William's list. Lewis traded primarily in allegory, the closest thing in fiction to non-fiction. And, in fact, much of what Lewis said in his fiction could have been said better in the form of the essay.
Williams may indeed be right that there are no modern evangelicals who can claim literary greatness. I suspect he is. But I have a protestant to throw into the mix--one who does not come from a liturgical tradition, although it would be flirting with credulity to call him an evangelical.
Berry's book Jayber Crowe, for example, would, I think, have to be classed as a work of Christian fiction. And, as a writer of Christian fiction, I don't see how you could exclude him from a list of Christian writers. I suppose someone might object that he is not a very orthodox Christian. I am willing to concede that point, at leas for purposes of argument. He is, officially, a Baptist, and attends, occasionally I am told, a moderate (or liberal, depending on who gets to label it) Baptist Church. He is, however, a member in good standing of a Christian denomination, and much of his writing deals in Christian themes (his environmental writing is certainly solidly planted in Genesis, for example).
The argument that he would have to be excluded would basically have to boil down to saying that, while he may be a Christian, he is not a very good one. Well, let' say that is true. Graham Greene could not be called a good Catholic, could he? Yet he would make anyone's list of great modern Christian writers. In fact, someone, somewhere, has asked the question, "Why is the best Catholic literature written by the worst Catholics?"
No. I will stand with Berry here as something of a counter-example to William's thesis that all great Christian writers come from liturgical religious traditions, although I do think his thesis is, generally speaking, a very good one.