The Aliens comics are great stuff. Book One and Book Two are definitely worth a read. Earthwar I didn't like at all due to the absolutely hideous art style it was drawn in which didn't allow for me to care about the story.
Personally, I'm a huge fan of Aliens. It's the quintessential sci-fi alien shoot-em-up, but I really think that it ruined the franchise.
Alien was amazing because it was a horror piece. The alien got very little screentime (in large part because they couldn't make it work as well as they wanted) and when it was seen, it was usually quick flashes from extreme distance or extreme close up, but its presence was palpable throughout the entire film; it was infinitely powerful and unkillable, like any good horror film baddie.
Aliens was just a shoot-em-up. Hordes of the once-invulnerable xenos getting blasted left and right just took all the power away from it as an enemy. So much so that they had to come up with an even bigger and badder version to try to recapture some of the feeling that just one of the creatures had in the original film.
I know you can't really compare different genres, which Alien and Aliens are, but I just feel like Aliens devalued the creature.