People crtitisize Wii owners for not buying more "core" games like this.. but if you owned a Wii, honestly, would you buy this game? Unless you're a HUGE Dead Space and/or light gun fan, the answer is probably no. Of course this game failed. It's an on-rail shooter in a sea of tons of other on-rail shooters on Wii. It may even be a great game, but the fact that it's an on-rail shooter alone usually indicates that it's half assed and probably not worth $50. I can can guarentee you that this game would have failed on ANY gaming console.
Make a Wii game that is fun, marketable, and worth 50 bucks, and the sales will come. Make a half assed effort at a Wii game and expect half assed results. It's as simple as that. I don't know why these developers cannot figure this stuff out when it comes to Wii development. The amount of effort a developer puts into a game (or lack of effort in this case) shows through in the final product, and the consumers can see through it.