I would have to agree about the Fallout 3 trailer. I had never heard of Fallout before that game, since I was never really a PC gamer until a few years ago, but when I saw that trailer, I instantly fell in love with it.
All the non-engine cinematics for dawn of war series are awesome, but mark of chaos intro is by far one of my favorites. What makes it even more awesome is that the priest of Sigmar sort of looks like Bruce Willis. www.youtube.com/watch?v=dNFGJQIW5ZM
Just think about bruce singing hymns for the glory of sigmar, as he strikes down enemies of the empire.