Brilliant summation Michael! For me I'd add that ALIENS is also the more dramatic and developed story. The characters have a dimension, dramatic arc, that does not exist in ALIEN, where it's just a group of "truckers in space" being picked off one by one. Ripley's character, her relationship with Newt, the maternal aspects of their scenes together, and even the fact that Bishop isn't just another "evil android" were all narrative surprises -- plus the movie wasn't just a group of action scenes or a recycling of the original film. It's a different type of picture, but I think Fox was wise to go with Cameron and not just make a sequel that would've been "more of the same."ALIENS is a film to be experienced, whereas ALIEN is a film to be absorbed. I guess that's how I would summarize how I feel about the two films.
ALIEN is like a painting from a master artist, a canvas that beckons you with its atmosphere and cinematography; ALIENS visually isn't quite on that level, but in terms of character and drama -- not to mention action -- I think the sheer nature of its approach lends itself more readily to repeat viewing.
Love them both though. In my little universe, the story ends with ALIENS and everything that came after is just a bad nightmare. lol.