Well, Ghost was arguably the most beloved character out of the Modern Warfare series. They even had a comic book series started after him and a lot of people wanted to have a game that featured him as well.
Lots of games have you play as characters that you either suspect are going to die, or know they're going to die, I don't see how that detracts from the game overall.
As far as the actual mask is concerned, yeah they could have done a better job (I've seen better on some graphics) but for the teaser trailer, it will do.
What I'm really wanting to see is that because they are going to fully reveal the game during Xbox's new generation reveal, if the rumors that a brand new game engine is true. Apparently it has been in the works for the past several years for this new console and hopefully it will help get the series back to where it used to be.