Without doubt, the most powerful game trailer at E3 was the one for Assassins Creed: Revelations. In a little more than three minutes it shows the scope of the game, its depth of character, its speed of play and the breathtaking world in which it's played. Really, it speaks for itself:

[youtube http://www.youtube.com/watch?v=6kL7ursHalk&w=560&h=349]

Some others:

The Final Fantasy franchise continues when the latest installment, XIII-2, arrives in 2012. Here's what it'll look like.

[youtube http://www.youtube.com/watch?v=Q-75BdU8U-w&w=560&h=349]

Paradox Interactive and Kerberos Studios plunge into more adventure with Sword of the Stars II: Lords of Winter. It's a stand-alone follow-up to the 4X franchise and "reveals the dark secret of the original series."

[youtube http://www.youtube.com/watch?v=Zvpada4dWM4&w=560&h=349]

Finally, I found the team-based MMO World of Tanks to be both ambitious and dramatic. It's about strategy as much as action though the trailer, of course, focuses on the latter.

[youtube http://www.youtube.com/watch?v=hJd9iCbpwuI&w=560&h=349]