To me Apocalypse is the greatest threat the X-Men have ever faced in the comics. Every time one of the X-Men's television iterations tackles the character it ends the series. What else is there to do after they face the first mutant? The most powerful mutant who has lasted generations? That being said I tried my best to separate my love for the comics and cartoons and let the film universe unfold before me, which I will say was a little hard because I was not a fan of the X-Men cinematic universe reboot that was Days of Future Past.
The film opens, in an amazing sequence, at the end of the reign of En Sabah Nur (Apocalypse) as he transfers his mind and powers into the body of a mutant who can regenerate. He is betrayed by the people who fear him and he and his Four Horsemen are entombed within a pyramid ending his rule of the land at its height. Cut to the 1980's where Charles Xavier has now fully set up his institute for gifted youngsters, Mystique is going around freeing mutants who are enslaved as a hero figure to her fellow homo superiors, Magneto has hidden himself in Poland under a new name and started a family as a mutant no longer in the eyes of the world and we see the birth of Scott Summer's powers as he becomes Cyclops. CIA operative Moira Mactaggert, who was last seen in X-Men First Class, is undercover in Cairo investigating a cult that worships the first mutant. She stumbles upon them as they reawaken Apocalypse from his tomb and an earthquake is felt around the world that sparks many of the characters in the film on their paths to changing for better or worse. As Apocalypse awakens he gathers the most powerful of his "children" he can find to become his new horsemen and cleanse the world of all its problems brought about by Homo Sapiens. The X-Men must reunite with new and old members in order to defeat Apocalypse. 
That is the simplest and quickest way I can describe this film. We are introduced to characters left and right some we have seen in previous movies and others are brand new. Honestly in this one it feels a little too much. It could could be argued the MCU gives us a lot of characters to deal with at once but the difference is each character is given their own film for the audience to connect with them that leads up to their Avengers films. While this is the 8th X-Men film if you count the Wolverine movies, the last film completely negated five of those previous films. So any character you were supposed to care about based on those previous films, most of that background is gone. They've changed the story lines, changed the dynamics and changed the actors. We have a new Nightcrawler, Storm, Angel, Jubilee, Jean Grey and Cyclops who have never appeared in this new rebooted series plus the introduction of Psyloche and Apocalypse himself. Oh and the worst cameo appearance of all time which if you blink you will miss him of the Blob as he falls unconscious into frame. That's a lot to juggle right there and there's still some characters that just seem to keep forgetting lessons they learned in previous films. I'll start with the good. 
Nightcrawler is awesome. He is an awkward little German guy who comes in with little jokes every now and then that play so perfectly without him meaning to be funny. His powers are shown excellently here especially since this is the first time he's expanded his ability to use his powers to their fullest potential. Cody Smitt-McPhee aka the kid from Let Me In is an excellent Nightcrawler. Once again Evan Peters steals the show as Quicksilver and every moment he's on screen you cannot take the smile off your face and for once you thank god that Marvel let Fox have Quicksilver in their Universe as no one is a better Quicksilver than Evan Peters especially with the best montage you'll ever get, set to the tune of Sweet Dreams! I'll probably be berated horribly for this but I never thought Famke Jansen was a good Jean Grey and was always annoyed by her on screen in the X-Men movies so when Sophie Turner came in to take over her character I was more than ready for it! She does a really good job bringing the strain of Jean's abilities to the portrayal of the character while not over acting and giving a performance that made me care for her character more than I have in previous films. 
X-Men First Class ended with the characters all having found out who they are and having absolute resolve in what they would do for the world. Then Days of Future Past came, Bryan Singer kicked Mathew Vaughan off the project, killed half the characters that weren't played by famous enough actors and decided that Professor X would give up and become a junkie, Magneto was tried for murdering JFK and then all of a sudden was innocent because why would he kill a human and then Mystique who was a stone cold killer in the original films was too timid to pull a trigger. Not to mention for someone who was "mutant and proud" she hid her blue skin constantly unlike in Singer's other films where she was blue 90% of the time. Then at the end of Days they all had their moments where they decided who they wanted to be, but cut to Apocalypse and the only one who stuck to their guns was Professor X. Magneto gave up, married a human and had a kid. Mystique is still freeing mutants but straight up says there's no reason to follow her or fight for the cause. I can kind and of live with that but this was the most boring misrepresentation of Magneto I have ever seen. The entire sequence with his new "family" is completely unnecessary. The idea is with him having something to lose can drive him to join Apocalypse but the man has already seen and lost enough to be angry forever! I was completely bored by this sequence and didn't care at all about his family especially when Quicksilver is half assedly set up to reveal he is his son in the movie. A point of which could have been a huge game changer for the climax of the film but is not used and never even resolved in the film. 
Also once again Jennifer Lawrence is too famous to be put in blue makeup for a majority of the film and apparently Nicholas Hoult's Beast is as well. I get it. Faces sell tickets and makeup FX don't but I'm paying to see the X-Men and to see their characters represented onscreen. We never saw Kelsey Grammer out of the Beast makeup! The rest of the characters are just kind of there with a few cool moments sprinkled throughout but nothing really to cry home about. Although apparently Angel is a drunk that likes to listen to Metallica's Four Horsemen which made me chuckle. The biggest crime though? Teasing us with Jubilee so much so that she is best friends it seems with the core X-Men kids, but we never see her use her powers and when the other kids go to fight she's just left with the rest of the students. 
Apocalypse himself was a lot better than I thought he would be. He looks really cool and in the first act of the film he is relentlessly brutal in dispatching anyone that might harm him or his children which makes it easy to see why mutants would follow him so easily. He unlocks their powers beyond their wildest dreams and shows them they are the strong that should inherit the earth as they had been prosecuted in his absence. Oscar Issac plays him really well and gives the character a very ominous look and feel. That's the first chunk of the movie though and in all honesty there is no reason given for his reawakening other than some guys praying at his pyramid and then all of a sudden he is awake. For the climactic battle he is kind of on the sidelines. When he finally does come out to fight it just seems far less grand than what it should be. For how many characters are in the movie and the franchise at this point, the battle with Apocalypse should've been all out war with everyone they have going at him with everything they've got in a merciless fight to end all fights! This is the 8th film! This should be the battle to end all battles but it just kind of gives way to a psychological battle that goes into a slight teaser for the next film. It's something we've seen already in another X-Men film and it was cool but I've seen it already, I wanted to see something new and crazy. The end battle just didn't cut it for me and made Apocalypse so much less epic than it should've been. 
Then of course we finally get the costumes we've been teased with in so many images that resemble the comic book costumes and the movie ends. The X-Men are back together which I didn't even know why they were disbanded in the first place and Mystique is helping Professor X lead them now. There was a lot of potential in this film but for every 10 minutes I enjoyed there felt like 20 minutes I just shook my head. It's a dumb fun movie but nothing really new and was very disappointing to me as a fan. There's one more cameo which the look of the character is fantastically spot on to the comic, but the entire sequence he is in is completely unnecessary to the plot of the film and felt like it was there literally just so they could put the character in the film. It's a fun brutal segment but I would have gladly traded it for more of the story that I paid to go see. A lot to love and a lot that falls short so the best I can say is 3.5 cool new mutants out of five.
