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!
From the list up there, I'd say "Remember the Time" or "Jam" -- but "Can't Let Her Get Away" is my favorite, probably because it's the first MJ song I found on my own since I stopped listening to him at about five or six. It wasn't the song that made me a fan, but it stood out to me