They tried to do it in America and failed multiple times through its unconstitutional nature. In England, however, there is nobody to stop the government from applying compulsory ratings on videogames, with legal ramifications for those who sell so-called "violent" titles to minors. With the Byron report coming soon, it is now fully expected that the government is going to step in and take some control over what content can and cannot be purchased.
In addition to this, Parliament is also expected to start handing out advice to parents, telling them to keep consoles out of kids' bedrooms and in the main rooms, lest they dare be playing that horrible, horrible Resident Evil when nobody's looking.
While this in no way affects the majority of gamers, who are above legal age anyway, and the BBFC's ratings already have legal implications, it is still worrying to see government take such a hands-on approach with peoples' lives. In no way should we be ruled over in such a manner, but it seems that it's going to happen, and that's one slippery slope. Furthermore, I believe that this focus on shielding children from the "evils" of games and movies is only going to do them more than harm in the end.
By all means, raise a child in a bubble and smother it in kid gloves, but as humans they are already inherently violent, and videogames can be a most positive outlet for one's pent-up aggressive instincts. I just don't think it's wise, at all, to pretend that violence doesn't exist, or that this type of entertainment is something that junior is not "ready" for. If it's kept hidden from a child for most of its life, when the time comes that it can finally choose for itself to indulge in "forbidden" entertainment, it will do so in abundance, and maybe not be able to handle it simply because he was never given a chance to. By banning a kid from certain games, we only make those games more romantic in its mind. I think these game restrictions will have the opposite effect than their intended ones, in the end.