Speaking of WWII games, Brothers in Arms is the best I think. Brothers in Arms 2 has some of the best AI I've ever seen. I'm a big fan of advanced AI. I was playing skirmish mode with a friend. It allows you to play split screen, one player commands a fire team, the other an assault. You can be either German or American forces. Anyway, we were playing as the Germans. The American squad came in behind our position from an alley of a village level. I moved my team around the building to flank their position. What surprised me is that they picked up on my move and moved straight in through the alley and did a full-out assault on my friend's position. By the time I made it back around he was almost dead. That's just an example of the awesome AI. The enemy forces will also move their positions further back if they feel they're going to be flanked, link up with another team, throw grenades, try to outflank your position, and perform all-out assaults. Yep, WWII is when true squad-based tactics came into existence, which makes for very engaging gameplay. Now someone needs to make a FPS based off of the Vietnam War, much like Battlefield Vietnam, but with GOOD AI, meaning smart and noncheating.