Wii is not for kids. Its fun for all ages, and in order to be fun for all ages it must have games for all ages. Consoles not really have an age target, what decides the age target for a console is the games that come out for it. If most of the games for one console are for one age group then people say that the console is for that age group.
The people who make games like manhunt will say that they are targeting over 18s but a good number of people playing the games are still around 12-16. And the people who make the games know this and make the game accordingly.
I live in the UK and lets take GTA ( or 2 or 3 or what ever version) for an example. In the UK it is ILLEGAL to sell GTA to anyone under 18. But most of the people that buy it are buying it for their kids (the parents) or their friends. People may point at a game like GTA and say that its not made for kids but it IS made for kids.
The wii has ended up being a games console for ALL ages. I have seen youtube videos of 2 year olds playing the wii and having fun, and I have read about how the wii has become very popular in retirement home.
