Why Start Story Trailers With Dialogue
I belong to the school of trailers derived from dialogue (as opposed to adding an omniscient "In a world..." style narrator or trailer with giant title cards which say something like “A HEARTFELT STORY…” Consciously or not, I think this dialogue based trailers tells the audience what they're seeing is unadulterated and genuinely representative of the game. Of course, editing can do a LOT to manipulate how a game is perceived, but it's less in-your-face than the alternatives.
A big reason I work this way is because of my love of movie trailers, and this is the way I learned to edit a trailer. A more practical reason is it's more difficult for me to write words out of thin air than it is to take words from the game, and either re-arrange them to tell the story, or use them as a first draft that I'll lightly modify to sound like a cohesive voiceover.
A drawback of this method of editing is I think it's not as easy to do when you're making a trailer for your own work (especially if you're the writer). Constructing a story trailer from dialogue often means breaking the lines down, divorcing it from its original context, and putting it in a different order. Lines within a scene can get shuffled around, or lines at the end of the game might be used for the beginning of the trailer.
For example, in the trailer for Star Wars: The Phantom Menace, Qui-Gon says "There is something else behind all this your highness, they will kill you if you stay." But in the film those lines are "They will you kill you if you stay... there is something else behind all this, your highness." This is a small example, but I can imagine George Lucas never even considering changing the order of those lines because in his mind they're cemented as is into the screenplay. But a trailer editor's outside perspective allows them to manipulate things even if they go completely against how they work in the full context.
This trailer uses a handful of title cards, but mostly uses the in-game dialogue as the base of the story.
Story trailers pieced together with dialogue allow the editor and marketing team to disappear behind the curtain. I think people appreciate when they don't feel like they're being marketed to even when they knowingly clicked on a video whose sole purpose is to market a game.
Unfortunately, I think it's also one of the most difficult ways to make a story trailer. If you look at the history of movie trailers, trailer voiceover dominated until around the 2000s. Part of this is likely due to the difficulty of editing on film vs using digital non-linear editing, but it could also be a sign of an industry improving their skills over time.
If you'd like to try your hand at this, here are a few posts of mine should help you do it!