But it can also lead to massive disappointments if the game doesn't stand up to the trailer (looks at World of Warcraft's beautiful trailers.)
Also, The Witcher 2 and 3 has some just amazing trailers. I really hope that 3 looks as good as in the trailers or really close to it.
I remember the trailer for Halo 4 and was like, hey, I've seen better CGI, then they announced it was ALL in game engine. I wish more companies did that. Otherwise it's like the Atari 2600 - amazing Box Art:

And little Squares Gameplay:








