Ask HN: What are the Great Agent-Simulation Games?

Given the general suboptimal performance of Sim City 2013, (which hopefully Maxis/EA will patch in the next few months) - What are the really great games that have intelligent path finding and individual agent behavior that you can observe. I have three favorites - Ceasar 3, Settlers 7, and Stronghold. What makes each of these great, is that you see this emergent behavior from your city, based on little more than the self-interested behavior of a small number of agents that you can watch scurrying around your town, picking up, processing, and delivering resources (some of which are then inputs into a another agent) What are some of the really great agent-simulation games that have pulled you in for many months?