Straight to business-
Alien: Picture is jawdroppingly good, yes there's some grain but people without huge bits of wood up their rears will get over that. Sound track & Goldsmiths film score are superbly done.
Aliens: For me the star for sentimental reasons. The picture is presented in 16:9 which will fit your whole screen & again the overall picture quality is stunning. The sound track & film score still put the fear of God into me.
Alien3: Personlly I think hugely underated, a worthy addition to the franchise. The transfer has come out really well & I think the best picture quality of the lot....& thats saying something. Sound track & film score are extremely engaging.
Alien Resurrection: I wish I could be enthused by this film, but i'm just not. It has it's moments i'll admit but on the whole I think they should have sold the story to Darkhorse comics as it feels very seperate to the other three. Picture quality is good & the soundtrack's nicely polished.
All-in-all a stunning release. The overwhelming thing for me was the attention to the soundtrack & film scores, it's been given the DTS Master treatment, just magic.
Oh & 60Hrs of special features. One of THE essential releases.