Projectile weapons in pressurised environments, whether on board a ship or in a different atmosphere on a planet might not really be the best idea. Something with less penetration/more localised damage might be the better choice.
That said, the Star Trek 'phasers'/'disruptors' etc etc are really pretty rubbish weapons in other respects. A projectile weapon such as a machine gun can fire dozens of bullets in the time your phaser has one little zap. OK, admittedly, you can't use a machine gun to heat a rock to stay warm or set the phaser's power pack to explode and clear a way out of a cave/prison cell/whatever. Similarly, projectile weapons probably wouldn't have the Star Wars blaster ability of either opening doors (by shooting the lock) or sealing doors (by shooting the lock).
I suppose the choice between a machine gun or phaser/blaster really depends on whether you want a straightforward weapon or a swiss-army gun.
For what it's worth, I think Aliens is an excellent film with few dodgy plot points (other than the fact that everyone and I mean everyone on the spaceship buggers off down onto the planet surface!), especially in comparison to some of the more modern movies around.
The limited Colonial Marine technology/weaponry is perhaps to some extent just a factor of the technological movie-making limitations of the time it was filmed. I have to say that Cameron didn't exactly cover himself with glory in Prometheus when he had a much freer creative hand due to CGI and the like. I know which of the two movies I'd rather watch.