Not to worry ...

... David Orr on The Great(ness) Game.

... Edward Byrne comments: Rating Great Poets and Considering Contemporary Concerns.

I think it's worth noting that in, say, 1880, an article discussing greatness in American poetry would probably have given short shrift to Walt Whitman and would not have mentioned Emily Dickinson at all. A look at a poetry anthology published in 1950 would reveal much about the evanescence of poetic fame (which is not the same thing as poetic greatness).