1. Phase 3 (2016 to 2019)
Captain America: Civil War
Guardians of the Galaxy Vol 2
Avengers: Infinity War
Ant-Man and the Wasp
Spider-Man: Far From Home
Phase 3 was truly the crowning achievement for Marvel Studios. This was the phase that Marvel had been building toward since the very beginning long before the Avengers ever assembled for the first time. It was the culmination of the 21 movies that each played a part, be it big or small, in building towards the Avengers final showdown with Thanos in Avengers: Endgame.
Endgame was by far Marvel's most ambitious movie ever and ultimately went on to become one of its crown jewels. The movie was crafted in a way that made it easy for newcomers to enjoy it, but that also found a away to pay tribute to the fans who had been part of the journey from the very beginning.
In addition to Endgame, Phase 3 also featured some of the best films the MCU has ever seen.
Captain America: Civil War pitted our heroes against one another in an epic showdown that introduced both Spider-Man and Black Panther into the MCU. We then saw these two heroes lead their own respective films which were each magical in their own regard, though the clear standout was by far Black Panther which celebrated the nation of Wakanda and its incredible heroes in one of Marvel's true masterpieces.
Captain Marvel and Doctor Strange entered the mix, the Guardians returned for another adventure (be it a lackluster one), and Marvel fans finally fell in love with Thor in what is hands down the best Thor film, Thor: Ragnarok.
One could fill pages and pages with highlights celebrating the films from Phase 3 which isn't likely to be unseated as the best Marvel has ever had to offer anytime soon.