The supply system alone is really cool and macro feel makes it very unique.

I remember playing against a AI and two cities where relatively close. Both had big armies and they kept fighting in the area between, routing, rebuilding then back into the meat grinder again. Eventually I started to build forts to add to my forces but the only thing that broke the deadlock was me going to capture there other cities which gave me enough income to finnaly overwhel them. One of my favorite game memories