I feel like Cities: Skylines has just the right amount of complexity. I recently went back to Sim City 2000 by comparison (which holds up!), and was taken aback by how much I had to divine (or remember) on my own. Not that it's a bad thing, mind, just something modern audiences have to take into account.
Skylines instead seeks to gradually ease you in -- it even limits the amount of land you can use at first. It has a calm feel to it, even before you head into the annals of its advanced machinations. Then again, every time I put a sewage disposal pipe upstream I scream out loud; there's always enough to keep you on your toes.
The new Mass Transit expansion adds similar wavelengths of zen and frustration.