Personally, I can't stand many of the "classics"! The Jane Austen types... Proper romancin' and such. Although this probably extends to modern works of romance as well!
Other than that, the classics are wonderful. Turn of the Screw, Island of Dr. Moreau, Candide, Don Quixote -- timeless! I was not overly enthralled by the many modern "classics" such as Gatsby, Catcher, and the like. Of Mice and Men... I've tried rereading them after they were blundgeoned into my head during those joyous school days; still to no avail. Overall I'd say I keep about the same ratio of likes/dislikes, regardless of whether the book is classic or not.