Bingowings said:

The Dead Island trailer is a great piece of total CGI film making (it has a strong emotional effect) but as none of what we see in it is in the game, other than zombies and the general idea of the resort, it's not necessarily a good enough reason to go out and get the game

That is pretty normal and acceptable for a game trailer. When a game is that far from release teasers like this are just released to generate interest and to get a feel for the market's interest. This was more of a "So, what do you think about this?" trailer, closer to the launch date you can expect some "Hey, you should buy this product we're selling!" ads.