I've spent many happy hours playing the original... My only gripe is that it always turned into a traffic management sim. Yes there were other challenges, but traffic was always front and centre. (At least for my cities)
Once I figured out how it works, traffic management became fun. And money-growing-management-stuff and the waiting is what ruined the game for me. So now I'm playing with infinite money and the only challenges are traffic and making stuff look good. Getting people to where they want to be with lane management, public transport networks, and bikes and pedestrian paths.
What is the challenges you prefer in city builder games?