Is Alien the exception to the rule?

Anyone who watches movies knows that several things are almost always true:

1)If it's based on a book, 9 time out of 10 the book is better.
2)Sequels are usually bad.. sometimes funny bad, but almost always bad. There is the occasional exception (thank you Godfather II fans), but generally speaking the higher the number (II, III, etc) the worse the movie is going to be.

I think I might have found the exception to the rule with Alien vs Aliens. Maybe because I watched them out of order (by accident!) I subconsciously found myself favoring Aliens, but however it happened I think I actually liked a sequel more than an original.

Not that Alien was bad- far from it- I just think that Aliens was better. In Alien we meet Sigourney Weaver's character, Ripley, and see the first installment of human vs alien. Although humans technically win the encounter, I kind of found myself annoyed by a lot of the crew members. I do have to admit that the first time one of those things bursts out of a chest it's both unbelievebly gross and pretty darn interesting, but this does not make up for the fact that the begining of the movie is rather slow. Maybe I'm showing my propensity for crass disaster movies.. but I was not all that enthralled by the ode to 2001 (lack of dialogue, slow start). Once the action gets going there are some pretty horrific death scenes, but I never found myself as scared or interested in the outcome as I did in Aliens. I did think it was interesting that there is an entire thread on imdb discussing whether an alien sexually assaults Lambert..but only becaue I found people's preoccupation with the idea kind of appalling. I don't think that the scene is question is meant to depict a sexual assault, I think it's just Lambert crying out as an alien scares her, slithers up her leg and then murders her. Do we really need to make murder somehow even worse?

Anyway, som things I learned from Alien:

1. Space food is gross. If you complain about it a lot maybe you'll put off imminent death..or maybe you'll just be lucky enough to die at the table!

2. I think that Dallas and Lambert might have been engaging in a torrid space affair. Maybe they snuck into those little space sleepers together. Anyway, based upon Lambert's totally hysterical reaction to Dallas's death I think they broke the sex rule and paid with their lives.

3. Aliens need oxygen to breathe just like we do! Thus sending them out into space is a surefire way to kill them despite knowing absolutely nothing about their anatomy or physiology.

4. Acid will drip through several stories of metal in a spaceship, but will conveniently stop right before puncturing the hull or injuring any of your crew members.