A lot of the Crysis AI's problems (in regards to the Koreans) seem to be related to terrain and environment pathing - the AI is actually quite good, but it seems to get confused easily by areas where there's lots of hills/differing heights of terrain. I don't get the omniscient AI thing Twenty Percent Cooler mentioned unless I play the retail game with no patches. I think at release CryTek upped the KPA AI's aiming ability because it was too easily confused by terrain and thus allowed the player to dispatch of them too easily.
I don't get this with the alien's AI: For me, I noticed that they almost never get confused unless in a confined space: I frequently have the alien Trooper/s get stuck inside the carrier on the last level, but when it's a relatively open room they rarely get stuck unless there's a lot of crates. Most of the AI used for both the Koreans/Aliens problems seems to come from terrain issues: When they're present without the terrain features I mentioned above, they work very well.
I don't why people hate so much on the first Crysis's AI: It seems to be like the Combine Soldier's AI issues in how they were actually quite smart, but terrain confused them to the point it heavily hindered their AI until Valve patched them, so they weren't confused by terrain anymore.
