I couldn't agree more about the disposable mentality. But I do think that in some cases, some stories are just too good to let go. And that is where you see two different mentalities behind various sequels and remakes.
Some remakes really strive to take a loved story and give it a new spin. And others just seek to remake an old film because they see the opportunity to potentially to rake in cash because of it.
For example, one of my favorite books as a kid was War of the Worlds. I also really love the old 50s film version. I think the fifties film version is fantastic, but when I heard Spielberg was making new version of the film back in 2004, I was very excited. It is such a great story, I felt a remake was a very reasonable thing. Unfortunately the new movies was pretty awful.
Essentially Indenpendance Day was also a remake of the 1950s War of the Worlds. I'd often talk my friends into watching the 50s version of WotW, and they would be stunned at how much is was like Independance Day. No doubt ID took a lot of inspiration from that film (which followed a very different path from the book), but the result was an enjoyable modern take on the story.
Several non-official sequels to War of the Worlds have also been written (including one that is a collection of short stories retelling the events through the eyes of famous historical world figures who lived during the time the novel took place, and their reactions to the alien invasion and their various attempts at coming up with ways to fight them). In some cases things like this are simply "cashing in", but some of this stuff was actually very creative.
A story like War of the Worlds is the type of great premise that simply can't be left alone. Too many people have too many good ideas on how to add their own spin to it.
Then you have a film like Planet of the Apes, which is also a really great story. But the idea of this being remade irritated me. And ultimately, it really ended up sucking. The original film is really the definitive version of the story. Sure it is based off a novel, but other than myself, I have never found anyone who has sat down and taking the time to read the thing. Most people experienced POTA through the original film. That film really struck all the right chords, and hit all the right marks. Why remake this film?
Magnificent Seven is another good example, there was nothing wrong with its source material. It simply took a great story, and gave it another spin. It lives in harmony with The Seven Samurai, and both films can be enjoyed side by side.
A film like Back to the Future being remade would be lame, because we already have a nearly flawless definitive version of the story. What could be gained via a remake?
A.I., while not the greatest film I have ever seen, was a very fascinating remake of Pinocchio. Imagine if Spielberg had simply decided to make another film about the wooden puppet? It would have been more of the same. Just another lame remake. Instead, it became its very own story, possessing its own good points and bad points.
I guess what I am trying to communicate, retellings of stories can be great, when they can bring their own spin to the tale and make it something that stands on its own (like The Forbidden Planet to The Tempest, or Chicken Run to The Great Escape). Rather than just re-filming what has been filmed with new special effects and technology.
In other words, remake does not always = crappy disposable money grabber, but more often than not they do. Same for sequels, some exist just for the sake of milking a little more out of an already successful film. But sometimes they are very worthy continuations of the original story.
Thus far, the current century seems to have been wholly devoted to remakes, sequels, reboots, spin-off, and adaptions or readaptions of well known books and comics. At this point, I think we are all pretty sick of it and are frantically reaching for the window hoping for a breath of freash air.