The RedLetter review of ST'09 had some good insights into this and the stunning statistic that 90%+ of the last few years' films have all been reboots. Wow.
Not stunning to me. For most of history, the majority of literature and drama has been retellings of existing stories. Shakespeare practically never told an original story in his life. Sure, today there are more original stories being created, and they're nominally the preference in our culture, but you're never going to completely get rid of a pattern that's been a part of human creative habits since the dawn of human memory.
Excellent point, there's only so many actual stories to tell, or so the story goes...but I'm not sure we're talking about the same thing.
It's the same way with musical theater as I recently found out while writing songs for a BMI workshop (which I didn't get into) - almost all musical theater is based on an existing story.
But there is a difference between a retelling of one of the stories humanity has always gathered 'round to hear, and a remake of one of those retellings.
The difference is that in the retelling, there is still some original & creative energy directing it. We could say that Luke Skywalker is a retelling of Arthur, and Obi-Wan is Merlin. And these types of stories go back to antiquity. But it's different to just keep remaking Luke Skywalker due to "brand recognition" than to find new characters, even if they are based on ancient ones.
Any snake will eventually shed its skin though.