I think his "Hobbit" scenes/dialogues are weaker because they "break" into the eddas-influenced prose of the larger narrative with a more "modern," perhaps more "petit bourgeois" speech, but some of his narrative descriptions are very, very well-done in terms of it echoing past styles without aping them too much.

I have my issues with Tolkien's LotR series, but I do think on the whole its prose is better than average for epic fantasies...and many other genres.