I thought that AvP actually could have been pretty decent with a few changes.
They should have never showed the Predators before the first time that a human character sees one. They could have built up a real sense of mystery and suspense with that huge, precise tunnel that was drilled through the ice before the humans arrived, but the audience knows exactly what's going on, since everything is telegraphed so far in advance. I know they included the scenes where the Predators come to Earth as fan service, but honestly, they made the movie weaker.
Also, the moment where the humans activate the machinery that starts the Alien breeding process could have been a huge "FUUUUUUUU" moment had it been foreshadowed and executed a little better, but it wasn't.
And of course, all the scenes before the humans get to Antarctica were completely terrible. They really needed a script doctor for those ones.
The movie had so little suspense compared to the first two films. Such a disappointment.