I don't know about "greatest" but I'll give you some of my favorites:

Blue Oyster Cult: Godzilla
David Bowie: Space Oddity
Neil Patrick Harris: Brand New Day
Sarah Michelle Gellar: Into the Fire
The Phenomenauts: Rocket Ride
Jeff Wayne et al: Forever Autumn and Thunder Child (from the War of the Worlds album)
Kraftwerk: The Robots