Totally depends on the kid. For DD, any Shrek movie, Cinderella, Sleeping Beauty, Beauty & the Beast (including the Christmas one), Mary Poppins, Veggie Tales, Elmo, Snow White, Little Mermaid.
For DS, Mater's Tall Tales (I'm surprised that DVD still works), Lion King, Madagascar, Pixar Short Films, Elmo DVDs, 101 Dalmatians, Lady & the Tramp, Dora, Diego, Team Umizoomi, Tangled, Fantasia (mainly the Fantasia 2000 -- especially "No Touch It"/"Green Girl" which was the Firebird Suite, along with the Donald Duck one and old Mickey Mouse Sorcerer's Apprentice).