If you want good AI in a space 4X then play Stars! Sure, you'll have to get over the interface design (the game was made by one of the Excel programmers), but this is bay12 after all.
An AI that:
Doesn't cheat.
Plays reasonably to its racial advantages.
Techs up reasonably.
Uses the parts this tech gives it.
Knows about minefields, stargates and stealth.
All this in a 20 year old shareware game.
Get it here:
www.starsfaq.com/download.htm#siteSure, sometimes it derps around a bit. Sure, you can beat it. But it can and will beat you. While you were expending resources on defeating one AI player, the others would be striving ahead, picking away at undefended planets, and your main fleets might be well out of position to respond. It thoughtfully is always set to "War", so the whole idea of diplomacy is pointless. I even hex edited the computer races a bit (into copies of my player made races) and they were friggen terrifying.
Could it mount major campaigns? Not really. But it could still surprisingly enough beat you. With enough of them against you. Once they had been "optimized", it could give you a pretty good game, even 1 vs 3. I can't think of any other 4X that can claim the same.
If ever there was a game that needed an update, this'd be it. Let's pray that one day there's Stars! the next generation or something. Instead of GalCiv4: "Last one was a whoopsie" edition.
Compare, contrast and complain. Or just talk about GC3.