My experience with Civ4 is that didn't 'cheat' outside of the handicap bonuses provided by the Difficulty Level. So yeah, it could have better production/tech/lower upkeep etc. And yes, it could start with additional units/techs on higher Difficulty Levels but all of that was 'above board' and easily visible in the settings file. It did not just 'create units out of thin air' or award itself techs at various times. With high enough espionage you could easily verify all of what an AI was doing (what it was producing, what it was researching etc). You could keep tabs on what they were doing and how quickly quite easily. Now if you're going back to Civ1 (and maybe 2), then yes, definitely the AI was not playing the same game the player was (however good the illusion). But Civ4 was a step up from that and it still played a very credible game by the end with BTS AI. Did it make mistakes and do dumb things? Of course. But it kept you on edge and many many times you would get very interesting wars with Civs who were technologically equivalent and competent enough to be a threat. Civ5 did this a bit in the first expansion but the 2nd expansion made it much more passive IME. I never played with the full 'Community Patch' AI so I don't know what the final result was. But Civ4, to me, was the pinnacle of the AI in the Civ series. It played by the same rules (other than the known handicaps) and still played well enough to keep the game interesting.