Keep in mind tho, that this list is NOT strictly adherent to the MCU's chronological order in the timeline (meaning you won't watch Captain Marvel right after Captain America: The First Avenger, just because they were the first in chronological order), but rather, I wanted a more cohesive experience in watching the MCU. I also kept every movie within their respective Phases, so there's that too.
Also another thing to note, is I left out Spider-Man: Far From Home out of this list, despite the film being part of Phase Three, because I wanted new fans to have a complete series to watch with a "definitive end" of sorts, and let them have the option continue with Spider-Man if they want to.
Another reason why I arranged the list this way, is because I wanted to slowly build off the MCU, the same way Marvel did so in the past, by introducing casual audiences first to heroes which are plausible in modern world (Captain America: The First Avenger and Iron Man), by focusing first on technology, science and good ol' heroic action. By slowly introducing fantasical elements later on (aliens, magic, space travel, etc.) new fans to the MCU can slowly get accustomed to their inclusion later down the line (that's why Captain Marvel is not suggested right after Captain America: The First Avenger). I also arranged the list in mind, to make sure each end credit phase would neatly tie into the next movie (ex. Captain America: The Winter Soldier's end credit neatly ties to the beginning of Avengers: Age of Ultron), so there's that as well.
Anyway, here's my list!
PHASE ONE
CAPTAIN AMERICA: THE FIRST AVENGER (2011)
Some notable ones are; the introduction to Howard Stark (Tony Stark/Iron Man's father), the development of the Super Soldier serum (which was revived again later on in Incredible Hulk), the existence of an Infinity Stone; the Tesseract (which appear again later in Iron Man 2, Thor and Avengers).
It may not be the most exciting MCU film in the Phase One lineup, but it certainly has alot of heart and good ol' fashion heroics to get even the most hardened of skeptics onboard.
IRON MAN (2008)
The great thing about following up Captain America: The First Avenger with this film, is the fact that it still keeps everything within the MCU grounded, and slowly eases up fans to more fantastical adventures to come.
THE INCREDIBLE HULK (2008)
Bruce Banner; upon exposing himself with gamma radiation and using a dose of the Super Soldier serum, first found in Captain America: The First Avenger, he becomes an uncontrollable monster who's power is fueled by his rage.
This is where we also first meet General Ross, who will return again in future installments of the MCU.
IRON MAN 2 (2010)
It reintroduces James Rhodes as War Machine, ties back again to Captain America: The First Avenger with Howard Stark and the Stark Expo. It also has some nods to Captain America, where if new fans never watched that film first, they wouldn't get the small easter eggs peppered in this film referencing that film.
This film also introduces fans to Black Widow who will be an important member for the Avengers later on.
The end credits also neatly ties in with the next film in this list...
THOR (2011)
Opening up that the world of the MCU has many other realms in existence, it finally reveals to new fans the existence of Asgard, a world where gods and goddesses are made real.
It finally unveils the origin of the gods first revealed by Johann Schmidt in Captain America: The First Avengers, and the ones who left the Tesseract under the care of humans on earth. It also introduces Thor, the brash prince of Asgard, who learns humility and earns his badge of honor and becomes a worthy hero in the process.
New fans are also introduced to Loki, which will serve as a recurring villain in the MCU, as well as Hawkeye who will be another addition for the Avengers team lineup later.
It's end credits also neatly tie in towards the events of the next film...
THE AVENGERS (2012)
Facing a threat from another realm, led by Loki, who was first introduced in Thor, the Avengers band together and fight against the Chitauri led by the god of mischief.
It reveals the existence of a second Infinity Stone, the stone scepter of Loki.
The movie is alot of fun, and is a great way to end the first Phase of the MCU, with alot of delightful moments and epic fights. Also fans get a first look of Thanos, the main big bad of the first 3 Phases of the MCU.
PHASE TWO
THOR: THE DARK WORLD (2013)
And while its not exactly one of the better MCU films in Phase Two or the Thor trilogy in particular, it does serve to expand the MCU by revealing the existence of a third Infinity Stone; the Aether. It also introduces other realms other than Asgard and Midgard (aka Earth), which would be further expanded in future MCU films.
The film also introduces the Collector, whom we will meet again later on.
IRON MAN 3 (2013)
While dealing with his PTSD, Tony is also faced with a new threat at home and an old rival who plans to take away everything he holds dear.
While not exactly a great Iron Man film, its still way better than Iron Man 2, in my opinion. While alot of people were let down with the main villain, I still feel its a great foil against Tony Stark.
CAPTAIN AMERICA: THE WINTER SOLDIER (2014)
Here, Captain America has gotten alot of time getting accustomed to his life in the modern day, and picked up alot of new tricks up his sleeve. The film gives Cap a much needed do over and reworks his character into a much more bad ass hero.
This film is also notable in shaking up the foundations of the MCU, with its shocking reveal and twist in the middle of the film, making fans question everything they know about the MCU as a whole.
The end credits of this film, neatly ties in towards the next film...
AVENGERS: AGE OF ULTRON (2015)
While it doesn't carry the same magic as the first Avengers film, this one certainly aged better, considering it pretty much set up alot of the things and laid alot of callback scenes that we will be seeing later in Avengers: Infinity War and Avengers: Endgame. Definitely a must watch.
GUARDIANS OF THE GALAXY (2014)
ANT-MAN (2015)
PHASE THREE
CAPTAIN AMERICA: CIVIL WAR (2016)
This film sees the return of General Ross (first seen in The Incredible Hulk) and pushes the Avengers towards accountability via the Sokovia Accords. This also introduces two new heroes into the MCU; first is the Wakandan monarch/mythical hero; Black Panther, and the long awaited inclusion of Spider-Man into the MCU.
The film features an ensemble cast that pits heroes against one another, in a battle that will divide the Avengers as a whole.
Its end credits lead up nicely to the next film...
BLACK PANTHER (2018)
Introducing fans to the hidden kingdom of Wakanda, (first brought up in Avengers: Age of Ultron)
SPIDER-MAN: HOMECOMING (2017)
GUARDIANS OF THE GALAXY VOL. 2 (2017)
DOCTOR STRANGE (2016)
THOR: RAGNAROK (2017)
AVENGERS: INFINITY WAR (2018)
ANT-MAN & THE WASP (2018)
CAPTAIN MARVEL (2019)
AVENGERS: ENDGAME (2019)
