Alien:
Main difference would be that the DC has the 'egg morphing' scene. In the TC she just runs pretty much straight to the shuttle.
Aliens:
In the Special Edition, we see the scene where Newts parents get hugged, and the sentry gun scene which you saw.
Alien 3:
In the AC, the Alien comes from an ox instead of a dog.
Res:
Barely noticable difference apart from the geginning which shows where the victims the Betty was transporting came from. At least I think it was them.
That's not every difference obviously, but that would be the easiest way to tell them apart.