We'll never agree on that one.
H.L. Mencken had him pegged when he said that his inverted sayings and epigrams eventually become just as mechanical as a preacher spouting platitudes.
(1) One reason why Mencken didn't like Joyce is the pro-Jewish sentiments in Ulysses - Mencken despised Jews, as his personal journals revealed.
(2) Mencken himself repeated inverted platitudes ad infinitum just to be cantankerous and contrary, so perhaps he was also jealous that Joyce both preceded and exceeded him in his metier
. Mencken delighted in mercilessly satirizing the land of his birth and in mocking the serious utterances of those dear to the "booboisie" using portmanteau words of his own devise. He was a second-rate Joycean in the guise of a critic, not a creator.
(3) Mencken thought John Fante was the greatest writer of the 20th century, so his general taste in fiction leaves much to be desired as well.