From what I've learned in my producing class, the reason why Hollywood keeps doing adaptations and remakes, instead of a lot more original movies, is because of risk vs. reward. Basically, when it comes to adaptations or remakes, there's a pre-existing fan-based and they know that those fans would go and see it, where as for original films, they do not know for certain if anyone would see it. Adaptations and remakes have less risk of losing money than original films.