I find City is strongest when there's one pile you already know is going to empty. Ruins in a Cultist game, Curses when there's a strong curser, Magpies, Wharfs, something like that. You know by midgame City is going to be Level 2, and then since City is such a great card, the city pile will empty and be Level 3. Otherwise City is a trap card, you're trying to empty the City pile by yourself, or some other pile by yourself (while still buying cities), and your opponent ignoring cities takes off faster than you.
One trick with Cities is to look for the card on the table that will allow you to Level up the cities on your own turn, to avoid giving your opponent the first turn with them. When the City pile is sitting at one City remaining, that Remodel or Develop you invested in can help you grab the last city near the beginning of your turn, and then you can play all your cities powered up before your opponent.