Australia is the only more developed country on the planet that does not have an R18+ rating for video games.  All of the reasons I have heard for this have been completely and utterly wrong.  I will carefully explain why each reason against an R18+ rating is wrong: 

1. It protects younger gamers from playing inappropriate games

No, it actually does the opposite.  There have been very few games that have been completely banned in Australia.  Games that deserve an R18+ rating make very minor changes so that they get an MA15+ rating.  This means that an R18+ game is only getting an MA15+ rating.  How exactly is that protecting younger gamers?  The answer: it isn't.  

2. They will have a bad influence on children

They aren't for children!  Do you show a child an R18+ rated movie?  NO!  Then why are video games any different?!  If a child is playing an R18+ rated game I believe it is completely the fault of the parents.  

3. If a game is refused classification it cannot be changed and then given an MA15+ rating

I'm sorry, but this just doesn't work.  It's not realistic and is basically showing all the loopholes with the current system.  Can you imagine games like Fallout 3 and GTA IV being completely banned in Australia?  The game developers will appeal the rating and offer to change certain things and will eventually find a way to sell their games in Australia, even if their game is far worse than the MA15+ rating would suggest.  

These are literally the only arguments I've heard and they're all wrong.  I will now explain why every reason supporting an R18+ rating makes sense: 

1. The majority of parents don't know that there isn't an R18+ rating

Several studies have shown that parents think there is an R18+ rating for video games.  This means that they do not realise MA15+ is the highest rating and most of games rated as such are basically R18+.  Some children take advantage of this fact and when a parent says they can't get a game they will say "it's not like it's rated R".  

2. Films get R18+ ratings, why don't video games?

Can you imagine what would happen what would happen if Australia banned R18+ rated movies?  There would be riots and violent protests.  There has been the argument that games are interactive and movies aren't.  But his is not always the case, not all games give you choice and a lot of them tell you what you have to do and there's no way of avoiding it.  

3. An R18+ rating will protect younger gamers

Parents will know that R18+ rated games are definitely not for kids and will make it a lot easier for parents to decide which games are appropriate.  

4. Games shouldn't just be for kids

Why should games by exclusively for kids and teenagers?  Adults enjoy video games just as much if not more than younger gamers.  In fact, the average video gamer is over the age of 18.  So, in fact, video games should be targeted at adults.  

5. If you're over 18 then you're missing out on games you should be allowed to play

Imagine someone made a great game that received really awesome reviews but was refused classification.  Imagine you're over 18 and was really looking forward to this game.  You are missing out because the government thinks it will give you violent tendencies and so that children cannot play it.  How is that fair?

6. I thought Australia was a free country

Since when can the government tell us what we are and aren't allowed to play.  Don't we deserve freedom of choice and don't we have the right to play R18+ games if we are adults?  

7. People will buy banned games illegally

If a really popular and critically well received game is refused classification then many gamers will do anything to get their hands on it, including buying the game illegally.  This means that the developer of the game is not getting any money from the people buying their game.  Police will have to waste time trying to stop this from happening.  

8. Educated parents will only allow there kids to play M, PG or G rated games

Parents that did know about the absence of an R18+ rating would also know that many R18+ games are getting MA15+ ratings.  Just to be sure, they would not allow there kids to play any MA15+ rated games just in case they should be R18+.  This would mean that they will only buy their kids, M, PG, or G rated games.  Games that were barely worthy of an MA15+ rating are treated the same as R18+ rated games.  Parents have no idea what games are appropriate for their kids whether or no they know there isn't an R18+ rating.  This might also cause games that deserve MA15+ to be downgraded to M.  

9. Adult gamers feel uncomfortable playing against younger gamers online

There are many adult gamers that hate playing with younger gamers online because they don't know if they should swear and feel they can't react if they are being abused.  If they were playing an R18+ rated game, there would not be many, if any, children playing that game and they will be happier and more relaxed.  

10. The classification board is not consistent

The classification board is biased in inconsistent with their rating of games.  They will ban a game for having too much violence but allow another game with the same amount of violence.  

The R18+ debate will be raging for a long time to come but hopefully the Australian government eventually realises that what they're doing just doesn't make sense.  It is better for everyone if an R18+ rating is introduced.