No 4X game I've played has AI that can reasonably take on a human without being given fairly substantial bonuses to it's ability to play the mechanics. In all honestly, I'd be worried if any developer could release a game that had human rivaling AI
Well, this is what I found to be the sad truth until about 3 years ago.
I am a programmer and in my job I work at something... boring. I really like 4x games but all of the ones I knew had incompetent AI.
I tried before with modding and could get some significant improvements out of Civ III and Endless Space-AIs that way. However, what could be achieved was limited.
Then I got Pandora: First Contact. I really liked the well-thought-out game-mechanics. But much to my dismay: bad AI once again.
So what I did was the following: I contacted the (Indy) developers, if I could get access to the code and work on it in my spare-time.
Signed an NDA, got my system set up and then started.
I worked on it for like 1 1/2 years during my spare-time.
Result is: AI is now better than that of any other 4x-game I ever played before.
The average player needs about 20-40 hours of experience with the game to have a shot at competing on the level where the AI has no boni.
We have renamed and rebalanced (toned down) boni on difficulty-levels twice. Even the highest one now only has a moderate advantage.
I can usually compete and win on the second highest about 50% of the time but on the highest I lost 7 games in a row with the latestes builds. With my 1500+ hours of experience in the game that is.
I contacted several big 4x-Youtubers if they'd showcase the game again with my final patch 1.6.7 (most have done so only on release... when the AI still was terrible) no response mostly.
Right now I'm working on a new 4x game, Dominus Galaxia. Once again an unpaid free-time-job.
The game has easier mechanics than Pandora and we are currently in Alpha about to release the first playable versions to a wider audience this month.
I've been working exclusively on the AI.
I have about 33% win-ratio against it on the fair level. AI development goes hand-in-hand with game-design here. For example we had to change how retreating from tactical combat worked because the AI was exploiting the ability to instantly retreat by trying to harass the player all over the place and you could not do anything to punish that.
It is really disheartening to read a thread like that and see how AAA-studios get away with utterly terrible AI.
But when I look at the feedback I've gotten for my AI-improvements for Pandora, I see why that is. The reviews got way more two-sided. On the one hand players who really like to finally have a challenging game with competent AI and on the other hand players who moan about how unfair the game is, beating them on Easy the third time in a row accusing it of having "ridiculous boni" even there.
Don't really know how to handle it. Personally I'm glad that I have at least these two games to play when I want a challenging 4x-experience and so it was still worth it somehow.
But it completely spoiled any other 4x for me. Not being able to tinker with the AI and make it play good is just too much of a disadvantage that no kind of cool game-mechanics can get me over with.
That being said: Doing a good or even great 4x-AI is possible. It's not a question of money, it's a question of dedication, intelligence and especially time.
Not doing a completely horsehockey one, that does mistakes so bad that it's immersion-breaking, on the other hand, is really inexcusible. 50% of the playing-strenght-improvement for pandora-AI came out of the first 2 weeks i worked on it, fixing the most glaring issues and using some-band-aid-placeholder-algorithms before making really sophisticated ones.