Your argument is a fair one: Many people would agree that Christie is "better" than Conan Doyle. Others would still see Conan Doyle as more important because he blazed a trail Christie didn't: He was the pioneer in the detective-novel form.

As for "grandmaster": Some people would still see that as sexist because of the "master" part, a masculine term. When I was researching this piece, I saw discussions of how we call men "masters" but seldom if ever call women "mistress," and that it's using a masculine term generically.

But all of your comments are reasonable, and I appreciate your making them in such an even-handed way. Thanks!