It is well nigh impossible to top the quality of feature-length titles like Curse of The Were-Rabbit or Pirates, just to mention a few, but The Flight Before Christmas, at 30 minutes only, comes very, very close.
Everything about this gem hits the mark: the story is touching, the pacing perfect (fast without feeling forced), the humor and characters without a single false note, the animation is amazing, and then.. the visual part, the look and feel of the christmassy, wintry world, interiors as well as exteriors, had me totally mesmerized. This looks so lovely and colorful, that I'd give anything to step into its magic landscape.
A classic? Yes, if there is any justice in the world, this IS a new christmas classic (also check out Robin Robin, another splendid Aardman gem on Netflix) and those who are untouched by this jewel in Aardman's crown are either dead or deaf n' blind.
By the way, there is a short Shaun title, from season 2, called We Wish Ewe(!) A Merry Christmas, that is just like this new only, a small miracle. Only shorter.