I like Predator 2, though obviously not as much as the original. They shoulda brought Dutch back for a sequel.
I've always been a bit annoyed at the Colonial Marines in Aliens. Those guys were way too undisciplined to be Marines... regular Army or National Guard I could buy... Unprofessional, too... why would they not figure out their appropriate weapons before hand? That should have been a basic premise of the mission planning. One would think they would have to have weapons suitable for fighting on ship in space (not punching holes in the hull is important!) and have the appropriate ammunition for it - no need for a completely different weapons issue. Of course, it shows the Cameron and Oliver Stone incomplete understanding of military professionalism, but they either sent the dregs of the Colonial Marines on that mission (with a wet behind the ears boot lieutenant at that) or it was a mission meant to fail by sending an understaffed incompetant undisciplined bottom 10%.
I like Alien 3, too... We all know how Fincher wasn't really driving the bus on that, but even so, there's much good stuff in there. I prefer the dog alien to the cow or whatever it was supposed to be, too.