My vote goes to Mizoguchi as well.  

Now, I passionately love Tokyo Story and Late Spring, and I've enjoyed just about all the Kurosawa I've seen (High and Low, Yojimbo, and The Bad Sleep Well are probably my favorites).  But let's be honest:  Ozu and Kurosawa, as great as they are, just aren't Mizoguchi.

Of the Mizoguchi films that I've seen, I consider Oharu, Sisters of the Gion, and Chikamatsu Monogatari the most impressive--and each, I think, is among the great masterpieces of world cinema.  (I should probably see Sansho and Ugetsu again, though.  It's been too long to trust my memory of them, and their critical standing makes me think that I'm probably underestimating them.)  