With games you always have to create illusions of complexity in order to get acceptable performance. Smoke isn't real smoke (no real time smoothed particle hydrodynamics) but instead you billboard couple of semi-translucant textures. Bullets don't use real physics, but act as a point mass with specialized collision detection mechanics. Enemy AI is often just a simple state machine and hacked together heuristics. Everything is fake.
With SimCity 5 you can easily have over 100.000 Sims in one city region. SimCity has to model the economy, happiness, education, water, waste, power, pollution, traffic, industry, and much more. So if you want to do this for 100.000 Sims in real-time you've got to cut many corners. There's just no other way. And the illusion in SimCity 5 is pretty damn good, from what I've seen. Cars drive with purpose from one place to another. Traffic congestion seems to make sense. Air flow affects pollution in a sensible way. Sure, there are a bunch of bugs but in general the illusion holds up. It's really quite impressive.
With SimCity 5 you can easily have over 100.000 Sims in one city region. SimCity has to model the economy, happiness, education, water, waste, power, pollution, traffic, industry, and much more. So if you want to do this for 100.000 Sims in real-time you've got to cut many corners. There's just no other way. And the illusion in SimCity 5 is pretty damn good, from what I've seen. Cars drive with purpose from one place to another. Traffic congestion seems to make sense. Air flow affects pollution in a sensible way. Sure, there are a bunch of bugs but in general the illusion holds up. It's really quite impressive.