Never. There is no real A.I in any game. It's just a bunch of scripted routines and responses, or predetermined actions that can give the ILLUSION of intelligence.
I've always had an issue with the use of the word A.I to describe how enemies behave. Also, I have issue with the way it is treated different in each game. Some games get slammed for bad enemy A.I, yet other games are let off the hook despite having atrocious A.I.
Look at the Call of Duty games - the enemies behave like IDIOTS - charging directly at me from hundreds of feet away firing a shotgun, or popping in and out of cover like a whack-a-mole carnival game. Yet no one talks about how idiotic the "A.I" in these games behave. The combine in Half-Life are similarly stupid. They never retreat - unless you throw a grenade - and more often than not, they'll just STAND there getting shot to death. Fallout New Vegas has stupid enemies as well: If I sneak attack and kill an enemy, more often than not his companion will be "cautious" for a few seconds then go right back to being completely unaware of any danger! "Dude, your friend's head just exploded, and now you're going to nonchalantly stand right next to his corpse, oblivious to any potential danger?!" is what I said when this first happened in FO:NV. Also, if enemies were truly intelligent, surely they'd put the facility on lockdown the very instant you killed an enemy, and they would be searching for the killer for literally hours! That has always bothered me in MGS games - you kill 2 or 4 guards in the first section, and the others in the rest of the level don't care or bother to check in on their radio! They also seem to lose all interest whenever Snake or Raiden escapes through a door. That's ludicrous.
I'm not singling out CoD or Half life or Fallout or MGS for bad enemy A.I. I actually love all those games. I love CoD, Half Life, Fallout and MGS. I'm just using them as an example to show how even the best games don't have smart enemies.
True A.I in games will not happen until they actually invent A.I. Until then, it's just a bunch of scripted movements, canned lines and predetermined actions.