In their best moments, 'The Lord of the Rings,' 'Spider-Man,' 'X-Men' and 'Pirates of the Caribbean' movies have delivered unforgettable adventure and escapism for audiences. Now, though, with the decade winding down and all four franchises sitting as nice, tidy trilogies, the question must be asked: Isn't three the magic number? Do we really need a fourth movie from any of these aging popcorn enterprises? The answer (in Hollywood, at least) is, of course, yes, but each franchise faces unique challenges moving forward. `Lord of the Rings'/`The Hobbit' The story so far: Director Peter Jackson's majestic and magical interpretation of J.R.R. Tolkien's epic is arguably the gold standard for fantasy-film franchises. The 'Rings' film trilogy piled up a staggering $2.9 billion in worldwide box office (plus more than $3 billion in DVD and other 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, director and adapted screenplay. The challenge: The bad news is Jackson won't be directing this time. The good news, though, is that Guillermo del Toro is his handpicked successor. After the unsettling and singular fairy visions of the Oscar-winning 'Pan's Labyrinth,' there's plenty of reason to get excited about the Guadalajara, Mexico, native's mighty imagination coming to bear on, say, the black forest of Mirkwood. Still, 'The Hobbit,' published in 1937, is considered by some to be Tolkien's literary warm-up act for his 1950s 'Rings' epic, which is more complex, darker and intended for an older audience. The stakes are high: 'The Hobbit' will be told over two films with a combined budget north of $300 million. The status: Work is well underway in New Zealand on 'The Hobbit,' although principal photography won't begin until April 2010. Major casting announcements are imminent (Ian McKellen is already in, as are Andy Serkis and Hugo Weaving, according to recent comments by del Toro in a BBC interview), and there will be plenty of time for fans to debate them -- the first of the two films isn't due until December 2011, with the sequel in December 2012. Jackson is onboard as co-writer and executive producer, and by all accounts, his working relationship with del Toro is a supportive and upbeat one. And, miraculously, the film seems to have finally escaped the dreaded pits of litigation; an ugly dispute with the late Tolkien's heirs was settled in September and Jackson's scorched-earth battle with New Line Cinema was somehow resolved in 2007 and now seems like a fading memory -- well, at least to all of us who didn't pay attorney fees. `Spider-Man' The story so far: Not that long ago, the standard assumption in Hollywood was that there were only two superheroes with enough general-audience appeal to carry a film franchise -- Superman and Batman. That changed in May 2002 when 'Spider-Man' swung into theaters and grabbed $115 million domestically in its opening weekend, a new record at the time. Unlike the majestic Man of Steel of Metropolis or the handsome billionaire prowling Gotham, this hero was a high-school nerd bitten by a bug. Not only did he fight villains, he had to contend with homework, money problems and a losing streak with girls. The franchise, directed by Sam Raimi and starring Tobey Maguire and Kirsten Dunst, has continued to soar commercially -- 'Spider-Man 3' in May 2007 again set the mark for the biggest U.S. opening weekend with $151 million (although 2008's 'The Dark Knight' edged it with $158 million). The challenge: A fourth 'Spider-Man' film is a no-brainer for Sony -- the web-slinger movies rank as the three highest-grossing films in the studio's history. But while the first two films were widely praised for their verve and heart, the third struck many viewers as noisy, hollow and disjointed. The fourth movie has other challenges: How many other ways can the relationship between Peter Parker and Mary Jane Watson be bent without totally losing its shape? What villain left on the list can connect with a wide audience? The status: In May, Raimi said that filming on the fourth film will start in February 2010. He has regrets not just about the third film, but all of them. 'What would I have done differently? I would have done everything differently, every single shot, I think, in every picture that I've ever made. Everything that I've done torments me.' `X-Men' The story so far: With the triumph of comic-book properties in Hollywood today, it's easy to forget how startling Bryan Singer's 'X-Men' was when it arrived in 2000. Sleek, sophisticated and respectful of its source material, the Fox film ran counter to the then-standard approach of turning comic-book adaptations into smirking cartoons that insulted loyal fans of the properties. The $75 million film made $296 million in worldwide box office. The sequel 'X2: X-Men United' arrived as one of the most anticipated releases of 2003 and finished with $408 million worldwide and better reviews than the first one. Singer left the franchise to take on 'Superman Returns,' so Brett Ratner ('Rush Hour') was brought in for the third movie, 'X-Men: The Last Stand,' which rolled up $459 million at the box office but suffered withering reviews. The challenge: The fact that the franchise's central hero, Wolverine (Hugh Jackman), was spun off into a lone-wolf film in 2009 suggested that the Marvel mutant team might be akin to an aging band that just watched its lead singer launch a solo tour. But in September, producer Lauren Shuler Donner, a key figure in the franchise, said that a fourth 'X-Men' film remains viable and, more than that, there are efforts moving toward that goal, although they are in very early stages. The status: Amid all the noise, the most interesting tidbit in recent months was the August report in Variety that Singer was flirting with the idea of directing 'X-Men: First Class,' which would be a prequel based on the popular comic book series and the draft script by 'The O.C.' creator Josh Schwartz. Later, Donner publicly stated that 'First Class' is not the likely next film, but the linkage of Singer to any Marvel mutant is big news -- and may signal an effort to have him back in X-business. `Pirates of the Caribbean' The story so far: Back in 2003, in the months before the release of the first 'Pirates of the Caribbean' film, few observers thought the venture was seaworthy. It was a $135 million movie based on a Disneyland ride -- a crass approach to filmmaking that had given the world the failure of 'The Country Bears' just a year earlier. On paper, it looked like madness, but, of course, it turned out to be a treasure map. Johnny Depp's Jack Sparrow, would become a signature character in modern popcorn-film history, while director Gore Verbinski tapped into a rollicking mix of adventure, supernatural thrills and comedy. The first film pulled in $654 million worldwide. The sequel did even better -- its almost $1.1 billion worldwide made it the highest-grossing film of 2006. A third film in 2007 brought in $961 million. A fourth installment, 'Pirates of the Caribbean: On Stranger Tides,' is due in 2011. The challenge: There are plenty. The first film was fresh, fun and unexpected, but the franchise started to get creaky as soon as it came back for a second voyage. The third film was oddly long and labored. Still, Disney wanted to keep this ship afloat, so a new approach was taken with this fourth film: The studio secured the rights to 'On Stranger Tides,' a 1987 novel by fantasy author Tim Powers that weaves a tale of pirates, voodoo and the Fountain of Youth, making this the first adapted work in the series. That's all to the good, but there's also the question of who will replace Verbinski, who decided that after three films it was time to go ashore. Rob Marshall ('Chicago') is the name that is everywhere, but his hiring has not been confirmed by the studio. The status: The plan is to start filming in the spring (according to an MTV interview with costar Geoffrey Rush). The venture got off to a sunny start when Depp, proving himself a real trouper, showed up at a Disney convention in Anaheim in his full Sparrow costume and makeup to promote the film. Depp and Dick Cook, the longtime Disney studio executive who was a key player in the 'Pirates' franchise, smiled, hugged and mugged for the cameras and fans. Then, just days later, Cook was fired by his corporate bosses. Depp, said he was 'shocked and very sad' and admitted that there was 'a crack in my enthusiasm' for the planned 'Pirates' sequel. But a contract is a contract, and few expect any mutiny from Capt. Jack. 