I played this game two years ago, and haven't watched the actual official trailer until today. I feel like this trailer does an excellent job at immersing a player into the universe of Bastion. The narrator is a character present throughout the whole game, and his low, mysterious voice and intense music sets a serious tone that hooks the player  into it. The gameplay they choose to show gives the player glimpses of the different monsters and weapons that is seen in the game.
So I think what made this trailer so successful is how fast the tone was set, the amazing consistent art style, excellent choice of highlighted gameplay and awesome closing with their logo.