Yeah i agree with all of that...

Over here in the UK, most games have a Pegi rating which gives the store an idea of which age group should be buying a game - but it doesnt stop anyone younger from buying the game...That could mean that 10year olds actually could walk into a store and buy a game meant for 16year olds and over....

Still most parents will willingly buy GTAIV and other games for their underage children anyway, so i dont know where any government thinks they are going with the rating system?
Also, kids whose parents do take note of the ratings system will still most likely be able to play these games. Be it at a friends house or a softer relatives? The fact is kids are going to get their hands on any game they want really, its pretty much impossible to stop at the moment...
Theres one more thing. Kids in the UK are allowed a debit card at the age of 11, so they could just order the games themselves off the internet without anybody knowing...

So the point is, in my opinion the ratings system should be improved as much as possible but do not expect that to stop a lot of children playing over-their-age-limit games. Its like films, kids can easily watch anything they want nowadays.