Is a bottle of wine an ideal 18th birthday gift?!

I'm not sure where you live but here in the States, the drinking age is 21. The fact that you say "mates" makes me assume a UK area. If you can drink at 18 there, then it is interesting. However, it depends on their personality. If one of them is a wine connoisseur, that may be an extremely appropriate gift (although I don't know any 18 year olds who are). Most 18 year olds I know are more into video games or things along those lines. So is it sophisticated? Certainly. Is it legal? Depends on where you live. Using your word choice: is it appropriate? Well that's up to you and if you think your friends are into that kind of thing.

Myself.

The French give wine to children at the dinner table at a young age, although they have less addiction problems than most.
It is not the alcohol its the personality that creates the addiction.
Just as a gun is not a killer its the person using it.
Is it also strange that a 18 year old cannot drink but can kill or be killed in some countries.

Depends on what wine it is. And as you have 2 mates then 2 bottles might be more suitable.

Not in the United States. The legal drinking age is 21.

No, Its illegal.

No, it'll be the beginning of an addiction.

they'll be having that anyway... maybe not wine tho... but try thinking of something else!

Yep!sounds like a good gift!