Given the fact Andy Muschietti's The Flash is essentially the third movie in Tim Burton's Batman chronology, it's at least partially surprising the movie has performed as awfully as it has. Of course, the reasons for this have far less to do with Michael Keaton's Caped Crusader than they do with the presence of Ezra Miller, innumerable delays, shoddy special effects, and overall disinterest with the DCU (or, rather, the former DCEU).
That said, at least The Flash does work fairly well as a chance to reunite with Keaton's take on Bats, making it perhaps the highest-profile indirect sequel ever made. But, Muschietti's film wasn't the first to seemingly be one thing before revealing itself as another (when The Flash was announced very few thought 'Well, here comes Keaton.') In fact, far from it, because even as far back as the '90s there have been indirect sequels and, for the most part, they're a treat.
9 Star Trek (2009) Is a Surprise Sequel to the Original TV Series and Movies
Accessible even to non-Star Trek fans, J.J. Abrams' reboot was a big success in the 2009 Summer movie season. The previews did a good job of teasing an impressive exploration, both visually and creatively, but they also teased a pack of handsome and beautiful stars fresh on the scene.
Fortunately for the audience, relative newcomers Zachary Quinto (best known for Heroes at that point), Zoe Saldana (who'd star in Avatar later that same year), and Chris Pine are far more than good-looking people. They're also masterful performers, and each one is perfectly cast in their lead roles as Spock, Uhura, and Kirk, respectively. Toss in phenomenal supporting performances from genre vets Simon Pegg (as Montgomery "Scotty" Scott) and Karl Urban (as Dr. Leonard "Bones" McCoy), and Star Trek is a ride worth taking over and over. This holds true for fans of the IP, who will almost certainly appreciate the Kelvin Timeline for incorporating Leonard Nimoy's Spock (or, rather, Spock Prime).
8 The Thing (2011) Isn't a Remake, It's a Prequel
2011's The Thing had such potential. Yet, the only element it truly has in common with John Carpenter's original is that both films flopped at the box office (and there are some very good performances, specifically the one given by lead Mary Elizabeth Winstead).
But, where The Thing fails is where it really counts: The special effects. Rob Bottin's prothetics work in Carpenter's original has a very fair claim to being the best in cinema history. Not just top-tier but the absolute very best. The 2011 film dives into the CGI pool, looking bad at the time and even worse after more years of technological advancement. So, while the third-act revelation that this film's events lead directly into the 1982 original is quite clever, it's also a case of too little too late.
7 21 Jump Street (2012) Is a Sequel to the TV Series
Metro-Goldwyn-Mayer
Phil Lord and Chris Miller's 21 Jump Street is something of a small miracle. Before it, Channing Tatum's reputation as an actor was...lacking. Jump Street showed that not only can he exceed as a co-lead, but he has absolutely phenomenal comedic timing. It also showed that a seemingly dead property can sometimes prove to be merely dormant instead. As long as an IP is continued in an interesting direction, audience's will consider it as something with more to offer.
Lastly, 21 Jump Street throws a legitimately surprising twist at the audience. Johnny Depp is virtually unrecognizable in his biker get-up unless the viewer is already looking for him. Even co-star Brie Larson didn't know it was him. So when Depp's biker reveals his true identity as Officer Tom Hanson (not to mention Peter DeLuise as Officer Doug Penhall), the film's revealed connection to the show is just the icing on a delicious cake.
6 Prometheus (2012) Is a Prequel to Alien
Some may debate whether Ridley Scott's pseudo Alien prequel Prometheus is an underrated one worth revisiting, but it does have its merits. For one, it's visually stunning and, two, it has some sterling performances, particularly Michael Fassbender's.
That said, it has some of the most unbelievably stupid characters ever committed to celluloid. Essentially, everything that goes wrong does so because a team of scientists can't make a logical decision to literally save their own lives. Heck, even Charlize Theron's Weyland Corp representative Meredith Vickers knows how to run a company, yet somehow doesn't know how to run either left or right.
5 Split (2016) Is a Surprise Sequel to Unbreakable
M. Night Shyamalan's Split stands on its own throughout the entirety of its runtime, save for the very last scene. Then, all of a sudden and much to everyone's surprise, there sits Bruce Willis' superstrong David Dunn, reprising his role from Unbreakable. A news report plays on the television showing how James McAvoy's "The Beast" has wreaked havoc across the city. A waitress comments how "The Beast" reminds her of another sinister figure from back in the day. She can't remember the name, but Dunn speaks up, saying it was "Mr. Glass."
As its own thing, Split works. And, back when first released, the film's twist was pretty exciting. Unfortunately, Glass was released three years later and made audiences wish Shyamalan had just left well enough alone, both for Unbreakable and Split.
4 A Mysterious Project Ended Up Being 10 Cloverfield Lane (2016)
Dan Trachtenberg's directorial debut, 10 Cloverfield Lane, didn't originate as a Cloverfield prequel, nor did prospective ticket buyers even know it was a Cloverfield prequel until two short months before its release. All they knew was that it was coming from J.J. Abrams' Bad Robot, it was ostensibly titled Valencia, and it had a small cast consisting only of Mary Elizabeth Winstead, John Goodman, and John Gallagher Jr.
They also didn't know it would be even better than the film that inspired it. 10 Cloverfield Lane is the small-scale version of the city-traversing original, and it's consistently buoyed by the strong work from the three leads, each of whom is given the opportunity to build a real character and does so with aplomb. Compare this to the fairly impersonal (even with a first-person style, which Lane mercifully drops) Cloverfield and you have a wonderful way to build a franchise. That is, until The Cloverfield Paradox stumbles along.
3 Ghostbusters: Afterlife (2021) Is a Sequel to Ghostbusters II
Jason Reitman's Ghostbusters: Afterlife did much better than Paul Feig's 2016 attempted reboot, and not just because the former project is the one that's connected to Ghostbusters and the slightly underrated Ghostbusters II (Peter MacNicol is great as is the bathtub slime scene). But it is connected, and even without the dearly missed Harold Ramis, Afterlife does a great job of feeling like a direct sequel to Ghostbusters II. It's just a direct sequel where the title characters don't show up until the third act.
One asset in Afterlife's corner is its director Reitman's obvious reverence for what came before. Another way of phrasing that is Afterlife was as much a passing-of-the-torch film behind-the-scenes as it was on the screen. It may have a slight pacing issue and perhaps a bit too much reverence for what Jason's father, Ivan Reitman, did with the first two, but it's overall a solid addition to the franchise, and one that fans had given up hope for long ago.
2 Spider-Man: No Way Home (2021) Is as Much a Sequel to Spider-Man 3 & The Amazing Spider-Man 2 as It Is an MCU Installment
Spider-Man: No Way Home checks every box it should and then a few more. About three to four years after the release of Sam Raimi's disappointing Spider-Man 3, no one thought there'd be another go-round for Tobey Maguire in the spider suit.
The same could be said of a potential third adventure for Andrew Garfield's Spider-Man, to whom No Way Home does even greater justice. The fact that the viewer learns of developments in both men's lives makes it as much a sequel as any, even if it's not technically their Spider-Man in the movie's title. No Way Home even revived interest in a third mainline installment for Garfield, but even if that project never comes to fruition Watts' film offers a fair amount of closure.
1 The Flash (2023) Is as Much a Sequel to Batman Returns as It Is a Solo Debut
Fans of Tim Burton and Michael Keaton's various collaborations are getting two sequels they've long accepted to be pipe dreams. First is 2023's The Flash, which serves just as much as a debut solo film for the titular character as it is a sequel to Burton's 1992 Batman Returns.
Second is Beetlejuice 2, and it seems a pretty safe bet that its domestic and worldwide totals will highly exceed those of The Flash. For one, The Flash tanked. Two, the original Beetlejuice is revered every bit as much as 1989's Batman. But, in the end, it's almost certainly going to be the presence of Jenna Ortega as the daughter of Winona Ryder's Lydia Deetz (assuredly an example of perfect casting if ever there was one).