For me you see the biggest difference with daylight and outdoor scenes, blue skies and what-not. The Shining is probably the most impressive one I've seen, and it's pretty cheap. That's a good one to start with. Don't get any bare-bones ones. Predator was really bad quality, but there's a new special edition of Predator coming out that looks promising.
Also I thought Enter the Dragon was really good, but last time I said that Chizzles said it had fake color. I don't know how he knows that, since you have to have seen it in the theater to see the original quality. I was -1 in 1973. it's really helpful to google reviews of blu-rays before you buy them. Some movies are no different on blu-Ray.
...Now I've seen your collection, I'd get the Ultimate Matrix Collection, the Spiderman Collection, T2 Skynet edition (on the main menu, Skynet figures out where you live and puts it on a map), and do you already have the dvd/Blu-Ray combo pack for Ponyo?
