There are many movies that over time become dated, either due to technology that was used during creation or that they were meant to be modern day and time has just passed. Then you have movies that while they could have been made different with new technology they actually hold up over time.
The best examples of these usually take place in some other place and time besides the present. That way the frame of reference is completely different than anything that we might have a reference to in modern day. Now just because a movie is dated does not mean it is not good it just means there are obvious dating issues from the movie. It is great to have a movie that holds up over time and can be watched over and over again.
There are plenty of movies that are rewatchable and hold up over time, particularly movies that tend to have an almost cult status among geeks. I wonder if some of the admiration for those movies come from timelessness. If a movie holds up over time it means that at any point in the future you can watch it and are not sitting there thinking about the fact that it was made in the 70’s, 80’s, etc. Now after a certain amount of times these movies become classics such as Casablanca, War of the Worlds, The Day the Earth Stood Still, etc.
I remember watching War of the Worlds for the first time (classic not recent) and while I could appreciate the groundbreaking nature of the movie, it was dated. You could tell the lack of technology available to make the movie and it was obvious it was an older movie. At the same time there is a point where it is so much older that it is classic.
The time where you can really tell if a movie is timeless is 10 to 20 years after it has been released, does it hold up against other things that you have seen or does it just seem dated. Now this is not talking about the look of the actors themselves, but it can be the clothing, the graphics, etc. There are many things that can date a movie, but if despite all that it still comes out as a good movie that you think competes in a way with movies now a days it has a strong chance to be timeless.
Think about Star Wars, even before all the CG was added to the movie, this movie stood the test of time. It is something that watching as a child and watching as an adult was just as good. The graphics might have aged a little bit, but the use of puppetry and prosthetics really help it to age more gracefully.
Movies that Age
Early computer graphics tended to be problematic when thinking about the rewatchability of a movie. When the CG was used to create whole creatures instead of just small green screen or adding extra dimension to the movies it tended to look like early CG which dated the movie. CG has made such amazing progress over a short period of time that movies that are just 10 years old can appear incredibly dated if there was an over-use of CG.
That is not the only thing, but I think it has meant that more recently movies can age quicker than they used to. Or there have been those movies, mostly made for tv, that skimp on the budget and therefore just don’t use the latest technology. This can make a movie age before its time. There are movies that are still very enjoyable even it is obvious when they came from, but it can be refreshing to not watch a movie for a long time and then when you do watch it again it does not feel as old as it really is.