Agricola, while I'm sure the fantasy genre wouldn't be the same without Tolkien, I don't know if it would be necessarily diminished, at least not greatly: for all we know, someone like Poul Anderson would've taken his place, and "The Broken Sword" would be "the" fantasy epic. I agree that the post-LotR fantasy genre is heavily influenced by Tolkien, but I reject the idea that without Tolkien there would *be* no fantasy genre.

"Tolkien, in addition to establishing the genre of modern fantasy (I’ve just had a lengthy discussion with my English major wife about the legitimacy of this attribution)"

Would you mind elaborating on how you came to this conclusion? If any one man could be considered the man to establish what we now know as fantasy, it would be Lord Dunsany (who inspired not just Tolkien, but pre-Tolkien fantasists like Howard, Smith, Merritt, Moore and Leiber).