AvP 1 had more plot than the entire franchises of Alien and Predator combined, and it didn't make the movie any less crappy. Neither of these franchises are about some epic quest that occasionally stops to play games at a casino. :rolleyes2 It's about suspense, the creatures, and characters. Plots disected, Alien was nothing more than a bunch of space truckers stumbling across the wrong distress signal and then dealing with a monster. What also makes the first two (and arguably three) Alien movies so endearing is the development of Ripley, especially when her bond with Newt comes into play. The rest of the casts, espescially Aliens' and Predator 1's, were very likeable and you really did not want them to die.
This is where AvP 1 failed, in my opinion. The main girl was not very likeable and the rest of the characters were hapless dudes with really, REALLY bad accents. If AvP 2 can turn this around, I think it will be winner since the action and creatures already look stellar.