Games with Good AI?

[Xanatos]

Ghost Recon (the first one) has the best friendly AI I've ever seen. They always do what they're told and are actually capable of self-preservation. Obviously they're not bulletproof and are just as vulnerable as the player - it is a realistic FPS, after all.
Unlike the newer GRAW 2 where your sniper has to go through 2 magazines to hit a target across the street and your team think it's a good idea to go prone in the middle of the road right in front of a Browning M2.

Crysis had some pretty clever AI too, although with your nanosuit powers it was hard to notice.