The marines got wiped out because they over-estimated their abilities.
They were convinced the mission would be a cakewalk. And, while they killed countless aliens in the process… they still backed themselves into a corner simply because they didn’t take Ripley seriously when she tried to tell them what they were up against.
Using the “alien” in the second film, had the marines actually been aware of the danger they were facing… they would’ve fared better.
Hell, the stand off in the second half of the film goes better then the initial encounter. With less marines. And that’s only because they didn’t run in thinking they were untouchable.
But even so, it makes the creature only deadly in large groups. Where as the reason the alien worked so well in the first film was because it was an unknown. You don’t get a good look at it, you don’t know what you can do against it… you don’t know what it’s goals are.
Something about “Oh, just shoot it with a gun… that kills it” takes away from the fear of the alien.
I like the second film, a lot (the original cut… not the director’s cut), but the first film is the best in my eyes. The unknown, the stealth and deadliness of the alien.
Also, I’m strongly with H.R. Giger’s opinion… I’m not big on the “redesign” of the alien in the second film. The original design is the best.