Metal Gear Solid 1.
"Hey what was that noise? Who's footprints are these?" Seriously, not even Kojima bothers with such amazingness anymore, it makes me a sad panda.

There are a lot of games where the AI isn't really held back because of how the game plays. So in these games, the AI is actually pretty good.

Most fighters have good AI on harder difficulties because it's coded in to predict your moves. You ever play Street Fighter 2 on the hardest difficulty and the moment you do something the computer always happens to block or counter whatever you do? It's because that single frame that you press the button, the computer knows what you did and the AI is coded to do this in order to counter. Atleast that's what I think they do.

For shooters I think the Uncharted games have the best AI.

all AI is scripted. thats how they make AI.

The Last of Us and Mass Effect 2 to some extent.

Lol, good one

Mass Effect 2 pfff

Skyrim.

Some of the AI in the Gears of War games was really good I thought. Maybe it was just me, but it seemed like some of the enemies made it really hard to hit them. They also do a good job of flanking you. There are probably better choices, but that's just one I haven't seen many people bring up.

FEAR. I never play it on higher difficulties, but the enemy AI was still incredibly sophisticated in terms of flanking maneuvers, especially in comparison to other games.