City view at the Conrad HKG means, I believe, a lower floor room (rooms start at the 40th floor) on the harbour side with the view somewhat obscured by adjoining buildings in the Pacific Place complex.

Mountain view means a view of midlevels up to the Peak.

Harbour view means high enough to be above the adjoining buildings, with a view of, you guessed it, the harbour.

Obviously harbour view is most desirable and much nicer than mountain or city views.
Rich