^Alien 3 is so underrated
But yeah, the first two are dead cert classics.
They're not all that dated really, perhaps apart from some of the hairdos. Most of the special effects stand up pretty well today. Partly because the creature and vehicle effects are physically based (i.e. miniatures, suits, animatronics), plus they were shot with a lot of style and moody lighting. Also because they were shot by A-grade visionary directors. Some of the composite work might look a little dodgy by today's standards, but still.
What's more, Giger's design for the alien creature itself, and his whole twisted artistic flair which inspired the aesthetic for the first film is purely masterful.
Well worth the watch indeed!