The Problem in Australia is that we don't have a R18+ rating for video games. This means that any game that doesn't fit under MA15+ gets banned. Fallout 3 fell victim to this for a while, and hopefully L4D2 will be the catalyst to finally get an R18+ rating here in Australia.
But we must look at the problem evenly. Already children under 15 are getting hold of games like GTA. We can't honestly say that kids will be getting hold of R18+ games and playing them. Also we should try to figure out why we need so much realistic gore. In my and several of my friends' opinions Call of Duty 4 had the ideal level of realism for gore, providing a visual cue to show that we'd hit the person, but not showing us intestines and so on. So ask yourself why we need gore for these games.
On the flipside, the majority of gamers today are over 18, and should be entitled to choose what to play on a free, open and democratic market. Why should gamers be restricted to kiddy friendly games? There's an R18+ classification for movies, an explicit classification for music, and no restrictions on books, so why should games be stunted as a medium?
I myself support the latter view.