In recent years, Grinch Night, Pontoffel Pock and some of the other late 70s/early 80s Seuss specials have gotten more of a following, mainly due to The Nostalgia Critic and memes. It's always assuring seeing the 'You put your glasses back on and face the facts!' meme on Tumblr every now and then.
I always thought it was clever how Seuss called his race of people 'whos', and them calling their outhouses 'euphemisms'. He gets right to the point, without using such obvious words.
But more underrated than any of those is Seuss' live action feature from the 50s, 'The 5000 Fingers of Dr. T,' featuring Hans Conried in the title role. He was made for hammy villains! In spite of its flop at the box office, he has said that it was his favorite role to play, and it shows.