“X-Men: Days of Future Past” combines the three almost distinct X-Men franchises: the Wolverine series, the original X-Men series from the early 2000’s, and the prequel series that was recently started with “X-Men: First Class.” As such, the film includes an extensive cast, including actors from all three franchises. It is also possibly the largest and most grandiose of all the X-Men movies. However, it is also the darkest, and possibly least fun of them. I would put “X2” and “X-Men: First Class” as better entries, yet this one comes in a close third place.

In the not-too-distant future, an army of indestructible robots called Sentinels have been programmed to hunt down and kill mutants. Eventually, they start to hunt down humans too, forcing all of the mutants to team up, including Magneto and Professor Xavier (who is somehow back from the dead after the events of “X-Men 3”). Their plan is for Kitty Pryde (who now has the ability of time travel) to send someone back in time in order to stop the Sentinels from ever being created. And that someone is, not surprisingly, Wolverine.

The idea of time-travel has been overused in movies lately, especially when it comes to major franchises. It seems to be a device that directors use in order to either reboot a series (J.J. Abrams’ “Star Trek”) or to erase the unfortunate mistakes of an earlier film. Here, it is a combination of both. “Days of Future Past” reboots all of the X-Men franchises, while also erasing some of the mistakes from “X-Men 3.” In a sense, it makes almost all of the previous X-Men films pointless. Why revisit any of those movies when we now know that none of them matter? “Days of Future Past” is now the only one that figures into the timeline. I wonder if this was the best decision to make by director Bryan Singer.

James McAvoy and Michael Fassbender play the younger versions of Professor Xavier and Magneto, respectively. Though they do not physically resemble the older versions of the characters, they make up for it with some great performances. McAvoy, especially, gets a significant role in the film, as Xavier starts to mature and grow with his power (at one point even having a conversation with his older self), to eventually become the wise, authority-commanding Professor Xavier that we know. Jennifer Lawrence’s role is also expanded as the younger version of Mystique, who, in blue scaly body-paint, is still every bit the action heroine that she has become identified with in movies like “The Hunger Games.”

In the opening scene of “Days of Future Past,” which begins in the future, we see the mutants taking on the Sentinels. There is Iceman, with the ability to create ice from his bare hands; Bishop, with the ability to absorb energy, and then redirect it at the bad guys; Colossus, who can turn his entire body into metal; Blink, who can create teleporting portals; Sunspot, who can turn his whole body into flame, and others. This opening scene is full of the thrilling, exciting X-Men action that is so prevalent in nearly every entry of the series. Yet, after only a few minutes, it subsides, only to be replaced by endless scenes of talking, explaining, discussing, and then, more talking.

By far the best scene of “Days of Future Past” is when Xavier, Wolverine, and Beast need to break into the Pentagon in order to set Magneto loose. To do so, they hire a mutant named Quicksilver, who possesses the power of super speed. At one point, they are fired on by a group of security guards. And then time stops, and we see the world through Quicksilver’s slowed-down perspective, as he lazily runs across the room, knocking down security guards, nudging bullets out of harms way, and even stopping to taste a soup being cooked on the stove, all while Jim Croce’s “Time in a Bottle” plays in his headphones. The scene is so ridiculously fun, that I almost had tears from laughing so hard. It made me wish that the rest of the movie was just as fun, rather than being endlessly dark and depressing.

Why do all superhero movies now need to be so dark? They are meant to be popcorn action films, and as such, should at least have a light-hearted tone. I understand and even appreciate when they tackle heavier themes at the same time, an example being “The Winter Soldier,” which felt like a superhero/espionage movie. Yet, it still managed to have a cheeriness to it as well. “Days of Future Past” contains almost no X-Men action, especially considering that it is an X-Men movie. There are plenty of scenes containing Sentinels brutally ripping mutants apart, but almost no sense of fun.

For those that enjoyed the X-Men films as a whole, “Days of Future Past” is at least worth watching. The special effects are impressive, especially with the Sentinels, and the acting is great all around, even with the actors that have a very limited role. The themes are deep, dark, and even thought-provoking. But, I still wish they had lightened up a bit.