It should be common sense that doing something that stimulates your brainpower, like Brain Age or Big Brain, is healthier for your mind than Resident Evil 4. Won't make you a genius or stave off disease, but c'mon. It's not like it's a thinly veiled lie about being beneficial.
Dude, people lose weight from fucking Wii Sports. I personally think it's dumb to expect the Wii to be an exercise device, but Wii Fit will be way better than doing nothing, and who knows how a Wii Fit regimen will compare to how each person would normally exercise. You could say the same criticisms about DDR, but it really can drop pounds on you.