This was really hard as the album has so many Masterpieces, not just great songs, but standouts and songs that are Michael Jackson fundamentals - I chose Who is it, because the whole structure, the story and his vocals that shift gears and range so quickly - and you can feel the tension in his voice.
Plus how can you not dig that video - the song is so deep and reaching too.
A very close second is Will you be there - amazing gospel and Melisma and Michael's voice at his finest and such a full rich song.
Give into me, Dangerous, Keep the Faith, In the Closet are also just pure masterpieces and Jam and Why you wanna trip on me are almost masterpieces!