@ Squilliam
I didn't say gaming is just for kids, I just said the Wii is relatively especially popular amongst young kids. That's not a surprise as according to Nintendo's own studies in the past, the GameCube userbase was almost entirely dominated by kids.
One caution though when talking about averages, having 3 nine years olds as your userbase and one 90 year old grandpa as your userbase, still means the userbase is dominated by preteens despite the average age may be 30. For example in this case crafting games targeted at 30 year olds would result in failure.
I am sure there are many adult gamers, for example potentially also gaming on PCs. But from what I have seen the Wii does especially well with kids (and females of all ages, the latter more so than I anticipated) and the 360 does well amongst young teen males. Actually most 360s I saw being bought here were for 10-12 year old boys when the console only was 119-149 Euro around here including taxes over the holiday season. As for entry pricing that's pretty cheap, for many cheap enough to buy as a kid's birthday present, for sinterklaas celebrations or for Christmas.