Madonna And Prince Get Physical

So, I'm listening to the All Madonna Station that is temporarily on AOL Radio and they go deep with a forgotten Prince duet called, "Love Song" from 1989's Like A Prayer. I remember being excited when I first heard about that duet, thinking it would be something special. Ah, if only. The song is mediocre, but hearing it again made me think of other "event" songs (or albums) that worked and didn't.
Worked
Neil Diamond/Barbra Streisand - You Don't Bring Me Flowers
Paul McCartney/Michael Jackson - Say Say Say
Bob Dylan/Johnny Cash - Girl From The North Country (from Nashville Skyline)

Didn't
Stevie Wonder/Michael Jackson - Get It (From 1987's Characters)
Grateful Dead/Bob Dylan - Dylan & The Dead (Album)
Whitney Houston/Mariah Carey - When You Believe

I'm sure there's millions more, but those have been on mind.