And a good game with a good trailer can do better than a good game with no or a bad trailer.
It comes down to money....any game with an expensive peice of marketing (like a cgi intro or trailer) has to make that much more just to break even (a trailer of DoW quality was probably around 500k - 750k). The budget is finite (especially ours), and spending that kinda' cash for something that adds nothing to the gameplay (talking functionality, not immersion) would be extremely foolish on our part.
Another problem with cgi nowadays is that it's 'old hat'...the was once a time where 3d in any-form was mindblowing. Now you have places like Blur and Square doing such AMAZING work, it's become aa artform that requires perfection to build the proper buzz, and again, perfection is expensive 
Don't worry though, we're putting A LOT of effort into what should be a fantastic intro movie...even if it's not exacly CGI.