A partial city building fan here. What makes City Building exciting for me was that I enjoy games which actually make me think and looking at how my city builds into a flourishing economy.
Personally, I enjoyed playing Tropico 3 and Tropico 4. The complexity and realism of the game really impressed me.
Just a summary, it's a game about building a city in the Caribbean during the Cold War period. Other than building a city, you have to manage the diplomacy between USA, Russia and Europe as well as keeping the different factions in the city happy. Building churches to appeal the religious people, having free housing to appease the communist and so on.
What I liked about that was the high level management required to rule the island. You have to plan how you want your city to develop economically and politically right from the start. Also, the game actually gives you a lot of freedom to control how you play the game. You can actually implement policies which helps to propel your island forward in a certain direction. For example, if I wanted the city to rapidly increase in population, I can basically allow immigrants, regardless of the skill level to enter the city.