I take a approach similar to Moe's script, but do it via creating a custom view that shows only movies/shows never played (by by restricting files displayed to those that have a play value of empty).
So for movies, I have a custom view Film that shows everything, watched or not, and another called Film+ that only displays unwatched movies only. As soon as they are watched, they disappear from the Film+ custom view.
It's especially nice for TV shows where the same scenario above is employed, but of course goes a little deeper due to series/season/episode. The outcome is still the same however, which is, for any series I dig down to the episode level, all that is shown are the ones yet to be watched. And as soon as I watch it, it disappears from the TV+ custom view. I've been doing this way for years and it works flawlessly and is invaluable for those times when a year passes between watching episodes for particular series.
