There are at least a dozen strong contenders, but I guess I'd go with either Ashes to Ashes or Sound and Vision.
Not sure about his “best” song, but I’ve come recently to realize that his definitive song thematically is Life On Mars, with his subject dreaming of a transcendence she doesn’t find in our world, or in the films she might hope to find it in. Alternately, Moonage Daydream.
With a career as long and diverse as Bowie's, it's difficult to pick just one, but "Ashes To Ashes" springs to mind for the way that it deftly updates his earlier classic, adding a new level of pathos to the story. "Station To Station" would also make my short list.
Ok, it IS a friggin great song! Tonight is a such a mood of different styles, Side B being better than A, imo. And I'd say for good or bad I think people that would generally not enjoy Bowie would probably like this album. This song definitely the best on the album I'd say.
