Is it the challenge that appeals in the human vs human philosophy or is it the fact that to win someone has to lose? Is the size of the smile measured by the number of frowns it causes? Then again, I may be an anomoly. I laugh whether I win or lose a fight. I'm just glad to log on from time to time.
For me, it is that AI is artificial and usually (in all cases where I have played games against bots, including ones with a mix of bots and humans such as Quake and Battlefield 1942) open either to exploiting predictable anomalies or completely screwing you no matter what you do because the bot is better than a human can be (such as in aiming and in perceiving enemies regardless of obstructions). Here are things that come to mind in no particular order.
A super high-skill bot probably wouldn't be deployed (at least not in numbers) as it would be no fun. The bots would just kill everyone all the time. Maybe there would be a spectrum of skill on the bots, but the average would have to be less than the skill of an average human player for the game dynamics and appeal to work.
So, bots with degraded skill would be used. Then you know that any bot you fight could beat you except that it is not playing to its full ability. It's like winning against someone who lets you win, or decides he'll fight you but only with a 1000 lb bomb attached, or at 75% throttle setting, or something lame like that. "Gee, I beat a bot. Yay for me."
Bots would likely have "tells." That and the fact that they would be adjusted so not to be as good as the best human pilots means that there would be a class of people (and not an insubstantial number, judging from all the milkrunners in the game) who would prefer to attack bots and run away from any humans they can perceive in the fight.
People would learn combat techniques to exploit the quirks of the bots. These might be very bad moves against humans. So, you are learning "wrong" skills. It's like when I played Battlefield 1942. You could set it up to have a bunch of bots in it to fill out a map when you didn't have enough players. You'd go out there, and once you knew the weaknesses of the bots, slaughter them. But then a human would show up, and your move to take out the bot would be horrible against the human, and you'd quickly die. So, part of the game became trying to judge if you are going up against a human or bot. That takes you out of the "suspension of disbelief" and out of the immersion. Also, I would occasionally fly the horrible aircraft in BF1942. But they were so bad that I decided not ever to fly them lest I pollute my reactions for Aces High.
Bots are OK for doing things that are boring and that no human wants to do (drive a supply truck, man some acks 24 hours a day, be a target, etc.). However, bots being your opponent in a contest of skill, where that skill is the heart of the game, is the lesser domain of the single-player offline game.
I sneer in derision at it compared to the greatness that is Aces High, a multiplayer game where every airplane you fight is flown by a human.
That is also why I like multiplayer Quake way better than Quake against bots, BF1942 against humans way better than against a horde of bots, Star Fleet Battles against other humans instead of against AI opponents, poker against a bunch of other humans instead of against my computer, chess vs. a human opponent instead of against a computer, etc.
