I just browsed the USK data (German age classification system) a bit and found this statistic about the shift of age ratings over the years:
It includes PC, console and handheld games, but no mobile games. The share of games suitable for all ages get smaller each year, because more and more arcade and puzzle games are released on smartphones and tablets instead of PCs, consoles and handhelds.
The I digged a little deeper via title search, where you can filter for platforms and age classifications, and made this spread sheet:
As expected, handheld games target younger / broader audiences than console games. Also expected: games on Nintendo systems target younger / broader audiences than games on Sony and Microsoft systems. Nevertheless, each PlayStation and Xbox system has many games suitable for children and teenagers. Wii U and 3DS are on a good way to offer a more versatile selection of games than their predecessors.
Keep in mind that games with USK 0 or USK 6 ratings are not automatically suitable for / targeted at preschool kids. The USK mainly rates the violence level of a game... puzzle games with difficult riddles and sport games like FIFA also get USK 0, even if little kids have no chance to grasp the game.
I also have no wish to conceal the fact that games which don't even get a USK-18-rating are left out in the spreadsheet. You can't search for them in the title search... probably to protect us from these harmful brutal games. ;) But it makes no big difference... as you can see in the upper statistic, the share of unrated games was always under 2% and shrunk each year, because publishers aren't allowed to advertise these games.
And here is the PEGI chart:
