Let It Go - Frozen: Indeed the best song for me. Truly awestruck and stunned by the scene where Elsa sings it and she builds her "ice-lated" castle.
When You Wish Upon a Star - Pinocchio: Honestly this should be number one. I still can't believe Let It Go is number two! This song is a solid classic while Let It Go is so overrated.
Reflection - Mulan: Mulan is so powerful because it's about a normal girl trying to find her place in a rigid society. It subverts gender norms and is less about the romance and more about the people.
Go the Distance - Hercules: This is by far the best song on this list, the best Disney song and one of the best songs of all time.