its hard to believe what the MCU would evolve into when the first Iron Man trailer dropped. So I decided to rate each movies importance over the past 10 years. THe movies in read are skippable, if you've never seen the MCU and wanted to play catch up. All of the movies in LARGE letters are the cream of the crop.
Phase 1
Iron Man - The MCU's life expectancy depended on this movies success. Without Iron Man there is no MCU.
The Incredible Hulk - Honestly, this movie feels out of place. If not for the end credits scene with Tony Stark, you wouldn't know this was part of the MCU. This should've been a reboot instead of a sequel to the Bana flick. I give Marvel a pass on this one because this was probably shot at the same time Iron Man was. This movie can be skipped.
Iron Man 2 - This movie gets a lot of hate, but it wasn't that bad. It's basically an extension of the first movie. What it did was introduce fans to S.H.I E.L D and black widow. It opened the door to an expanded universe
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Thor - This movie can be skipped. Even though it introduces fans to the expanded universe, you don't really need to see it. Had they stayed in Asgard, for most if not all of the movie, that would've been better. But because of the Iron Man 2 end credit scene, it wouldn't have made sense. Even the easter eggs, became a non factor (the infinity gantlet being shown with all of the infinity stones in it). The only real reason to watch is to find out why Loki is the bad guy but that can be explained in 60 seconds. Hawkeye's intro is so insignificant, you don't need to watch.
Captain America: First Avenger - Its a period piece movie, which causes it to lose some replay value. It's important because it introduces Captain America, but I would have to say its skippable to a certain extent. I would recommend watching it. ALMOST every character dies once they fast forward to the present, so their importance in the MCU is non existent. Don't really have to watch. Especially, since they do a flash back of how Cap got to the present in the Avengers movie. HOWEVER, Bucky is in this so obviously this is a must watch before you delve into Phase 2
The Avengers - Classic. The first big budget team up movie that meets expectations. It introduces a new Bruce Banner which immediately makes you forget about Norton's role.
Phase 2
Iron Man 3 - I think this movie was made because it was an contractual obligation. Basically a filler episode. The only real importance from this movie is the fact that Tony finally got the shrapnel removed from his chest.
Thor: Dark World - It's important because it introduces another infinity gem, but again, it felt like a filler episode. The problem with making a Thor movie where you have him on earth is doing an injustice to the character because of how powerful he is. The forced awkward love interest also brings down both movies thus far. The villains in both thor movies are forgettable as they never got a chance to shine.
Captain America: Winter Soldier - Classic. It wasn't just a dope super hero movie, it was a dope movie in any genre. It opened up a new lane and it also led to the disbandment of S.H.I.E.L D.
Guardians of the Galaxy - Dope movie. The MCU at this point had built up equity with fans and were allowed to think outside the box and be more creative.
Avengers: Age Of Ultron - I think the vision for this movie was too ambitious. I think it should've been done in 2 parts, but because Marvel had already mapped out a bunch of other movies, they simply took out stuff to condense it and never really allowed it to be made the way it should have. Because of the east eggs and jewels in this movie, it has to be a must watch though.
Ant Man - Another dope movie that was a risk but turned out to be a sleeper classic.
Phase 3
Captain America: Civil War
Doctor Strange
Guardians of the Galaxy Vol 2
Spider Man
I didn't want to type for each movie, but I didn't put any in red, which speaks to the level of quality Marvel has put out from the first phase to this one. The only meh movie could possibly be Guardians. It was never going to live up to the first movies expectations, but it still was a dope movie for the Easter eggs alone.