Geoff Boucher writes: This week we’re taking a look at four major trilogies from this decade that are looking to add a fourth film despite substantial challenges — not least among those challenges the skepticism of moviegoers who may wonder if some of these Hollywood vehicles are running on empty.

The story so far: Director Peter Jackson’s majestic and magical interpretation of J.R.R. Tolkien’s epic is arguably the gold standard now for fantasy-film franchises. The “Rings” trilogy piled up a staggering $2.92 billion in worldwide box office (plus more than $3 billion in DVD and others ancillary sales) and also pulled off a magic trick that has eluded the “Star Wars” or “Harry Potter” franchises — it cast a spell over voters in the marquee Oscar categories of best picture, best director and best adapted screenplay. More..