The film that elevated the Avengers franchise from merely enjoyable popcorn flicks to outstanding cinema. I saw this 3 times in theatres, including twice on opening day. Even if you don’t particularly care for superhero films, you’ll likely enjoy Infinity War.
One thing to note: to appreciate the film to its fullest, it’s recommended you watch most of the Marvel Cinematic Universe (MCU) films that were released before it. Otherwise, it would be a bit like watching Return of the Jedi before the rest of the Star Wars trilogy. Sure, you could do it, but you won’t get as much out of it. Please don’t be put off by this! It’s well worth it – most of the MCU is great, and even at its worst it’s still enjoyable.
These are the films I'd say are required viewing beforehand, listed in order of release: Iron Man, Captain America, The Avengers, Captain America 2, Guardians of the Galaxy, Avengers 2, Ant-Man (optional – it’s needed for Endgame, however), Captain America 3, Doctor Strange, Guardians of the Galaxy 2, Spider-Man: Homecoming, Thor: Ragnarok, Black Panther. Also, be aware that Marvel films always have scenes after the credits – and sometimes more than one. While some are just for laughs, others are actually important to the story.