I had to double-check if it counts as "this decade" (February 6, 2010) but The Disappearance of Haruhi Suzumiya is my top animated movie of the decade, although it's definitely not a self-contained movie and requires extensive knowledge of the existing Melancholy of Haruhi Suzumiya characters to fully appreciate.
For self-contained movies, possibly Frozen even if it's probably an unpopular movie to still admit to liking, though I really need to see Your Name and In This Corner of the World again soon.