Quite simply, what trailers did their job and made you want to buy the game? Even if you would have brought the game anyway, what trailer just made you determined to get a game?
mine would be;
the e3 Fallout 3 trailer
http://www.youtube.com/watch?v=iYZpR51XgW0
the Skyrim teaser
http://www.youtube.com/watch?v=hGMOMkACtn4
the Sacred Ashes trailer for Dragon Age Origins
http://www.youtube.com/watch?v=-iFrHRaH0Os
the Destiny trailer for Dragon age 2
http://www.youtube.com/watch?v=jlACgYHtWCI
(what can I say, RPG trailers are the best)
mine would be;
the e3 Fallout 3 trailer
http://www.youtube.com/watch?v=iYZpR51XgW0
the Skyrim teaser
http://www.youtube.com/watch?v=hGMOMkACtn4
the Sacred Ashes trailer for Dragon Age Origins
http://www.youtube.com/watch?v=-iFrHRaH0Os
the Destiny trailer for Dragon age 2
http://www.youtube.com/watch?v=jlACgYHtWCI
(what can I say, RPG trailers are the best)