Yeah, I know, AI isn't just "one thing." But it really is the one critical missing piece here. Here comes some more observations:
Challege: Currently, the only way to lose is to start right next to a "godlike" AI and have them very slowly dismantle your empire despite the fact that they have an 8000 power rating compared to your 50, and they have 250,000 power fleets surrounding your empty planets. They just... can't figure out how to send transports. Once in a while they come. If you survive this initial push into the 3rd and 4th X's, you've won. The enemy starts deadly, and becomes more and more stupid as time goes on. The player, however, tends to have exponential growth throughout the game with a MASSIVE jump in power once all techs are researched. I'm talking... building 1million power fleets every few turns, that have no maintenance, and pulling in enough money to buy planets from other civilizations with great ease. It's GREAT to have all those tools available. But the AI simply does not use them. They don't focus enough on building powerful, FULL fleets, they don't adapt to your weapons/armor, they mindlessly attack targets they have no hope of defeating, and they leave juicy targets untouched, and juicy planets uninvaded.
Diplomacy: There is one AI setting for diplomacy. It's the same AWFUL system used in Fallen Enchantress. Is the player too strong? WAR! Is the player too weak? WAR! Is the player trying to win? WAR! Is the player my good friend who has helped me time and time again? WAR! But then 2 seconds later... oops. The player is too stronk. We surrender! Our terms? NOTHING. We offer NOTHING in surrender. We're basically just hoping you're in a good mood. Players want to build lasting friendships. Players want to be rewarded for good behavior, and punished for bad behavior. Also, can we get some theatrics? Some character development? They're all the same. Yes, the Drengin leader keeps talking about how he's going to eat you, and the Thalans keep talking about how humans are going to destroy the galaxy. So boring. How about some dialogue options that are meaningful? How about more complex diplomatic tools, treaties that are truly reliable and significant?
Power Rating: Player power rating is totally skewed. You can just manipulate it by pumping up your income. That's a false show of power. It severely overvalues income and undervalues industry, morale, culture, population, and research.
Hard Caps on certain ship abilities: Some unreasonable ships the player can easily design:
1) A sensor ship based on your homeworld that can see the entire galaxy.
2) A transport that can reach any planet in the galaxy the turn it's built.
3) A single carrier that can annihilate the most powerful fleet that this slow-witted AI could possibly muster.
"Modify" the galaxy more: GC2 gave players the ability to destroy stars and mine the asteroids. In GC3, players can't do ANYTHING to the galaxy. All we can do is mine resources. (this is really cool but...) How about star system destroying? How about asteroid mining? How about ways the player can manipulate or harness nebulae, black holes, and dead planets?
Galactic Projects: What happened to these? Yeah, you get a few in the very very late game, but by then the winner is already decided. (If you're at late game, the winner is the player.) Need a lot more of these.
THE GOOD: This game could be incredible. Here's a list of stuff that is really awesome in GalCiv3.
1) Resources. Um, awesome. I just wish they could be used for advanced weapons/armor, beyond just the early game "prototypes."
2) Ship design. Excellent, even better than GC2. Such great options for components. My one wish - more variance between mass/energy/missile.
3) Fleet design. So great, I love how you can passively control the outcome of battle with smart positioning, tactical speed, and ship roles.
4) Adjacency bonuses to planet improvements. LOVE IT.
5) Population actually affects raw production. Absolutely brilliant.
6) Precursor artifacts are REALLY good. That's cool - too bad the AI doesn't realize it.
Anyway, I could probably go on forever about this. Forcing myself to stop.