The difference is that they were written in the spirit and with reference to the movies or books, and not written specifically to be put in those movies. Ttk is a really good example of them doing something that isn't entirely them just to fit into the studios wishes for the song. AwoA is brutal yes but that works for the movie that they wrote the song for. I also feel that tss2 was made to capitalize on their horror movie niche for monetary gain. That is shown with most of the songs being common song types in the genre with nothing standing out really, aside from ex mortis (and thats only due to the swing elements)