Ok so I heard that COD 4 is amazing, but also that some of the 'amazingness' is lost on its DS counterpart. You should be aware that there is no online play, which for a game like COD 4 is completely inexcusable (especially given that metroid seems to have pulled it off so well). There are a few other complaints about the DS version, so maybe think twice before you buy it, or compare reviews.
Search Results from Metacritic.com
The DS version scored a full 20 points lower than the PS3, 360 and PC versions, so something has got to be up.