I told you, i get to drive this time
It's tough to assess the intelligence of GTA IV's enemies comprehensively, since you can outsmart some opponents easily enough by waiting for them to break cover or dumbly expose a limb, letting you shave slivers of health, one at a time, from their circular health meters. On the other hand, occasionally you'll spot an enemy doing something inexplicably intelligent, like hugging cover responsibly under heavy fire or after losing half his health, at which point extraction can be tougher than burning out ticks. Frequently you're also deposited in situations pitting you against a dozen gunmen, or forcing you to attack in adverse circumstances (while moving on foot or in a vehicle), which more than offsets any accidental or intentional emasculation of the AI. Regarding friendlies, I've read complaints about the partner AI "breaking". For instance, your pals refuse to follow you through a doorway. That never happened to me. My guys were always solid backups, and the only thing I had to make sure of was that Niko provided sufficient cover when his compadres would on occasion elect to rush oncoming or enfilade fire to break an obvious stalemate.