IMO, GalCiv 2 Ultimate Edition has very good AI. It plays ALMOST like a human player.
In my experience, it knows how to develop its colonies well, and comes out with strategies on the fly to counter what you are trying to do.
That is why I am still playing GalCiv 2 UE on different days.
GalCiv 2 has a lot of refine features, strategic options and more depth than GalCiv 3. But that is because GalCiv 2 has 2 expansions and the AI has been tuned over the many years.
On other days, I play GalCiv 3 because of the following cool features:
- Adjacency bonuses (IMO this is the best feature of Gal Civ 3 as it gives players strategic planning on colonies)
- Nicer graphics
- Strategic resources & relics
However, if I have to pick the AI between GalCiv 2 UE v2.04 vs GalCiv 3 v1.03, GalCiv 2 wins hands down.
GalCiv 3's AI does the basic things right. The issue right now to me, is that the AI is still not able to make full good use of the new features of GalCiv 3.
I'm sure though that when GalCiv 3 reaches v2.04, the AI will be many times better than GalCiv 2's AI.
Meanwhile, if I want a more refined AI experience, I play GalCiv 2. When I want to immense myself in the new features and do not mind the not so refine AI, I play GalCiv 3.