the correct answer is - It Does Not Really Matter!! When you are on the ship and wanting to look at the port areas, Deck 10 is the place to be. Easy access to both sides of the ship and at most a 800 foot walk from forward to aft.
That being said
Naples - In looking at my pictures - Port. But the bay is a huge horseshoe shape, so from either side you will see land. and my memory says that the view of the castle was off the back of the ship.
Civitavecchia - DOES NOT MATTER. you're docked in the middle of a huge industrial port - nothing to see here
Livorno - Not been there so IDK
Villefranche - The ship is at anchor out (way) in the harbor - so it most likely depends upon winds, wave and tides, on which way the ship is facing