@Vael: Thank you for responding, Vael. You know, I'm not certain that your assertion is entirely correct--that the a-intels of these other genres do nothing more than merely react to player-actions. This seems especially true in the case of the rts. Let's take a look at the very, very old classic rts, "Starcraft," and compare one of the ai behaviors between this game and C3C. Now Starcraft may not have a great ai, but in some respects, the game demonstrates better ai and mind you it did come out years before Civ3.
Civ military units should have all the same kinds of general abilities and behaviors as Starcraft units are supposed to have. But they don't. I'm not referring to any specific ability, like the ability to cover your enemy in a mass of goo. I am talking about general stuff. For instance, both games use transports to ferry troops across gaps in land terrain. Now, let me share my observations on how the ai of these two games differ in their approaches to transporting.
By the mid-late game in Starcraft, on maps where transporting is necessary, the ai frequently attempts to rally a large and varied force at some specified site from which the force will board a fairly large number of transports that will take them to or behind your front. Btw, by varied force, I mean a nice combination of melee, ranged, and specialized units. The transports are sometimes sent to a destination outside your perimeter where they unload the entire army, at which point the amassed land units begin a combined assault. Otherwise, the fleet is sent directly into the heart of your defensive position and the army is unloaded where you are most vulnerable. After the units are diembarked, the fleet returns home where they ready a second wave if necessary. This is what the ai seems to attempt anyway.
In C3C, however, the ai most frequently uses the following tactic. The entire beach-landing assault force consists of a group of two, four, or eight ships--half of which are transports carrying just one land unit and the other half being an escort ship. Once the assault team has disembarked, the transport and escorts return home to ready another wave, thereby leaving the land units without the aid of bombardment defense from the escort ships. Furthermore, because ships take a long time to cross most bodies of water and the ai does not use any exploits, your forces are able to annihilate the invaders before the next bunch arrives.
The problem here is that unlike in Starcraft, C3C does not rally a large fleet of transports or embark more than one unit. The cost of building a large fleet may be one prohibitive cause which means that although vbraun's idea of separating the ai into components are a good idea, we shouldn't think of each branch of the ai as utterly separate. Whatever the reasons may be, I think that Civ4's ai modders could learn a lot from observing the ai of games from other genres, especially from rts's--genres which specialize in one of the many aspects Civ4 will employ.
@Brain: Brain, I apologize if you think I am hi-jacking this thread. I hope you don't mind because it seems like a related and relevant topic.