Yep, it can get stale. Kingdoms of Amalur was my most recent world saving adventure that I couldn't care less about, mostly because of boring characters and mediocre presentation.
An odd thing to say about A Song of Ice and Fire, however. The sheer number of giant plot twists and major character deaths that that series dumps on us, makes it quite impossible to predict who will save the world, I think. Especially, after the introduction of the boy in the last book.