Each Halo game has had some sort of introductory cutscene. Halo: CE had the discovery of Halo aboard the PoA. Halo 2 had Thel. Halo 3 had the Cortana Monologue and Halo: Reach had the foreshadowing.
However Halo 4 had something better. The history of the Spartans, talking about their humanity. This fit the theme of the game well because much of the story revolved around the humanity of John.
However Halo 4 also suffered from some storytelling aspects. Many people who didn’t read the books were very confused. As a lore junkie it gets very old explaining what happened between Halo 3 and Halo 4 plus the events during the Forerunner Saga.
To prevent this confusion and help people understand and like Halo 5 more, have the introductory cutscene be a short summary of everything that has happened between Halo 4 and Halo 5. This will help the “lol why isn’t Chief with Infinity. Where’s DeMarco? Why is the Spirit of Fire there wasn’t it in that other Halo game?” Just a quick, 5 minute CGI cutscene giving a visual of all the events that transpired. After all if someone can do a Crash Course Halo in 5 minutes, why not a few years of Halo in five minutes?