AvP2's interactivity is what did it for me. In AvP1, you never had the option of using Harrison to unleash a multitude of facehuggers on a company security team.
Both were still good games, but I still prefer the second. The first did have a better atmosphere and was more intense. AvP2 was just more interesting.
Probably the worst one I played was PCJ. The gameplay is average, but the story is freaking ridiculous. Porn star assassins? Come on.
It makes the story of DOTS seem appealing.
Extinction was repetitive, but it was still way better than anything in PCJ.