The Flash and Legends of Tomorrow are taking a week off, presumably for Valentine's Day.
This one had the unenviable task of introducing Thor to the Marvel Cinematic Universe. Thor in the original comics was a man named Donald Blake who found a stick in a cave and striking it three times, it gave him the appearance and power of the legendary Norse god Thor, the stick becoming his hammer Mjolnir. Eventually, the comics revealed that Asgard was an actual place, and eventually rewrote it that Donald Blake was actually Thor in exile the entire time. It got complicated as the comics eventually tried to make it so Donald and Thor were different people.
The movie streamlines it by having Donald and Thor nearly unrelated, with Donald Blake being entirely offscreen. When Frost Giants invade Asgard during Thor's (Chris Hemsworth) coronation, Thor, his brother Loki (Tom Hiddleston) and the Warriors Three and Lady Sif use the Bifrost to attack Jotunheim. Being stopped and reproached by Odin (Anthony Hopkins), Thor is banished to Midgard, also known as Earth, where he encounters researcher Jane Foster (Natalie Portman) and her team. Thor has to learn how to be worthy of his hammer again before he can return to Asgard, hopefully in time to save it from the schemes of Loki who orchestrated the Frost Giant invasion so he can take the throne.
Personally, I love this attempt to reconcile the grounded world of the MCU which had previously worked with technology and science with the fantastic realms of Asgard, reinterpreting the myth of Yggdrasil as a cosmic nimbus connecting the realms, which can be easily accessed via the Bifrost. Thor acts as a fish out of water, putting a spin on stories like The Wizard of Oz in which a normal person visits a fantastic world, this time being a fantastic character going to a normal world.
So, does it work? I've yet to see a compelling reason as to why it doesn't. There's a clear plot: Loki, being told since childhood that he will always be in Thor's shadow, conspires to get Thor out of the way. Thor has to address his own shortcomings, so there's also some good character development going on. Add to that a healthy dose of action, fantastic visuals, some excellent music and you got yourself a good time.
The First Avenger takes quite a few cues from the revised version of the character seen in Marvel's alternate Ultimate universe. Instead of being a kid Cap recruits as his partner, Bucky Barnes (Sebastian Stan) is now the longtime friend of Steve Rogers (Chris Evans), who continually tries to get drafted to fight in World War II despite his clear physical limitations until someone decides to make him the guinea pig of an experiment to enhance soldiers, turning him from a scrawny little guy into a physically perfect soldier. Instead of having a secret identity as in the original Simon/Kirby comics, Steve openly works with the military as in the Ultimate comics.
The movie has its own twist by having Steve begin his post-serum career as a mascot for the armed forces, intending to encourage goodwill, until he discovers Bucky's regiment has been either killed or captured and—with help from SSR Agent Peggy Carter (Hayley Atwell)—he breaks away from the army to rescue the captive soldiers, including Bucky, but runs afoul of Johann Schmidt, the Red Skull (Hugo Weaving), the head of just divorced from the Nazis scientific group HYDRA.
The movie is directed by Joe Johnston, who also directed 1991's The Rocketeer, which also featured a WWII-era world with a good old American guy using a special weapon to fight Nazis. Also, both movies are a lot of fun with some great special effects when you decide you can enjoy them. I've heard criticisms that movie was nothing more than a prequel to The Avengers as it establishes the Tesseract, which comes up again in that movie, as well as introducing Captain America. But honestly, it's a story worth telling. Steve Rogers begins as a man who believes he has nothing to lose and wants to help fight in the war, then later, he discovers he actually does have something to lose, and has to decide to give it up for the good of the world. It's not about how a man became a hero: it's about how he always was a hero and how he was able to put that drive to good use.
Following from Thor, Loki (Tom Hiddleston) has met with a mysterious alien who has equipped him with a spear that grants him control of people's minds. He infiltrates S.H.I.E.L.D. and captures the Tesseract along with Clint Barton (Jeremy Renner) and Erik Selvig (Stellan Skarsgård). S.H.I.E.L.D. calls in Black Widow (Scarlett Johansson) to bring in Bruce Banner (Mark Ruffalo, replacing Edward Norton from The Incredible Hulk) as Phil Coulson (Clark Gregg) convinces Tony Stark (Robert Downey Jr.) and Nick Fury (Samuel L. Jackson) warms up Steve Rogers (Chris Evans) for the mission. Meanwhile, Thor (Chris Hemsworth) is on the lookout for his brother.
The movie works not by having the Avengers work as a whole but by having them address why they don't easily work together. About midway through the movie, the team manages to capture Loki, but their personalities clash with each other in a way that ends disastrously, forcing the heroes to finally pool what they can offer to stop Loki's plot and recover the Tesseract.
Taking on a movie like this was ambitious, but Marvel wisely laid their groundwork and got good storytelling. Someone who hadn't seen the previous five films is given enough information about the characters that they can go in blindly and still understand the story. Seeing all the previous films only enhances the experience. An exciting, stirring, well-paced film, what more can you ask for?