I would just say never having seen any of the Alien sequels or the one predator sequel. I saw the first Alien when I was very young. It made me scared and gave me nightmares. Of course I was 10 years old DUH! No films give me that feel anymore especially sequels.
I would just say that I loved this movie enough to go see it two times on my own. The movie was about an hour and a half long which is more than long enough for a fight between aliens and predators. I found the background of the "Predator" much more exciting and intriguing and I found the ties to Weyland Inc. very understandable and that there was a lot of visual queueing in it as well that the posters here obviously missed.
I don't think of this as an Alien sequel and I am glad it's not. I hope they do a second movie that fills us in on more things. I like the new relatively unknown cast members in it a lot. It was a lot like Jurassic Park (but with aliens and predators)..
You miss a lot if you don't see it more than one time. Especially about how they link the predators and aliens to earth's civillization.. I think I am going out and getting all the alien sequels on DVD now and watching them because I liked this movie so much..
I think the posters set their bars too high to what they were expecting because this has all been done before. It's easy to slam a movie because it's not the storyline you are used to seeing. But I loved it for what it was. I think the new female star is just as interesting and maybe more sexy than Ripley..