By Neil Smith
BBC News entertainment reporter
The fourth Harry Potter film, The Goblet of Fire, is confidently expected to break box-office records when it opens in the UK on 18 November.
The stars of Harry Potter have been signed up for one more film
Directed by Mike Newell of Four Weddings and a Funeral fame, it will be the fourth hit in a row for its young stars Daniel Radcliffe, Emma Watson and Rupert Grint.
All three have been signed up for the fifth film, Harry Potter and the Order of the Phoenix, due out in summer 2007.
By then, however, the series' status as Hollywood's pre-eminent fantasy franchise may be under threat from another blockbuster saga looming on the horizon - The Chronicles of Narnia, which is released in the UK on 8 December.
For three consecutive Christmases between 2001 and 2003, audiences flocked to see the three instalments in Peter Jackson's epic Lord of the Rings.
The first two of these, The Fellowship of the Ring and The Two Towers, opened in close proximity to the first two Potter titles, the Philosopher's Stone and the Chamber of Secrets.
The first Potter narrowly outperformed Fellowship at the US box office, but the situation was reversed the following year.
Their success proved there was a strong demand for epic adventure based on popular fantasy fiction.
And it is precisely that demographic that Walt Disney Pictures and its producing partner Walden Media hope to target with their $150m (£85m) version of CS Lewis's Narnia adventure, The Lion, the Witch and the Wardrobe.
Like the Lord of the Rings, the film is based on a 20th century literary classic and has been mostly shot in New Zealand, on soundstages previously used for Jackson's films.
But with six more Narnia books optioned, the nascent franchise has even more material to draw on than the JRR Tolkien-inspired trilogy.
As in JK Rowling's Potter books, the lead Narnia characters are children caught up in spectacular adventures involving witches, magic and outlandish creatures.
Tilda Swinton plays the White Witch in The Chronicles of Narnia
Where the Narnia series differs is that the children do not feature in every book, meaning any sequels would not be as reliant on specific child actors as the Potter films are.
Time has been a pervasive factor in the Potter series, with Radcliffe, Watson and Grint all ageing faster than their fictional counterparts.
One more outing is guaranteed, but it has been suggested that the series will need to be recast by the time the sixth book and the as-yet-unwritten seventh instalment are made into films.
That is not a concern for the Narnia series, whose real star is Narnia itself - a mystical landscape where animals can talk, mythical beasts are common and pools become portals to different worlds.
It is a complex setting that has more in common with Tolkien's Middle-Earth than JK Rowling's relatively insular Hogwarts.
And, like Middle-Earth, it comes with its own detailed history, geography, mythology and even cosmology.
It remains to be seen how much of this will feature in the first Narnia film, which is being pitched to audiences as a fast-paced, effects-based action adventure.
It is notable, too, that while Walden Media have optioned all the other Narnia books, a follow-up has yet to be announced.
Note also how the producers have opted for the most familiar of Lewis' series, rather than its chronological prequel, The Magician's Nephew.
It is a decision that reflects the fact that - outside of devoted readers of fantasy literature - The Chronicles of Narnia remain something of an unknown quantity.
Narnia tells the story of four children transported to a magical kingdom
"This is really the only Narnia book to make," says Chris Hewitt, associate editor of Empire magazine. "I don't think the others made that much of an impact."
Despite the name recognition, however, Hewitt expresses some pessimism about its chances.
"I don't think there's a huge buzz around Narnia," he says.
"There's no Lord of the Rings this year for the second year in a row, so our readers want something to fill that gap.
"But I think Harry Potter will be the more successful of the two - and while Narnia could be a good one-off instalment, the world's not really waiting for a sequel."
In the end, though, a third candidate - King Kong, Jackson's first film since the Lord of the Rings - may prove a bigger hit than both.
Wizards and witches are all very well, but on or off the screen neither would stand much of a chance against a 25-foot ape.