I think I was 12 when I started roleplaying, and despite some other, shorter campaigns we've played recently, the first campaign is still running.
First, it was just a let's-have-some-fun (with character sheets and dice, of course) thing. The characters resembled us quite much, in other forms and another world, though. I admit giving little thought to my character until I grew older, and those things have caused some difficulties now that we should at last be able to think that our characters make even some sense as persons and are credible. For example, what was the point in my character cooking his fellows some disgusting organs for lunch, wanting to eat this innocent little kitten, committing crimes without a reason...?
Reading through my old roleplaying-related notebooks, also my own growth can be quite clearly seen. The character is still stupid, childish, ridiculous &c., but maybe it's just a part of his personality.
Our group has remained the same for all these years, but it was actually by chance that it ended up consisting just us four. If I remember correctly, Lommy had tried to recruit some others from our primary school class as well, but we were the only ones to show enough interest & find the time needed... And I doubt we would now be this good friends if not for the roleplaying. Despite all the quarrels we've had, no one has had the gut to quit playing. And spending much time together has brought us quite close to one another.
Our long-term campaign is set in Middle-earth, but it's the only one. The others we've played together have taken place in various other fantasy worlds or a world invented by the GM herself. I admit I like Middle-earth the most. It has always fascinated me more than the stories themselves, and it's just wonderful to actually get there, despite it being a version slightly perverted by the GM's evil mind.
Other fantasy worlds work as well (although I always face the problem of not knowing as much about the place as my character should), to some extent, but I've found that games set in the GM's imaginary world are not quite my cup of tea. Because of the lack of information. Because I have no clue about what my character could be like if I don't know about the world first. And a world created by an average 17-year-old doesn't match the world creating of which Tolkien spent all his life.
I've never been much into computer roleplaying nor CCGs, but in my early teens I had a short craze for Middle-earth: the Wizards. I knew the rules but usually we just played a very idiotic variation with our own rules. Now I've happily forgot them both. Larping is not something I've tried, either. I've never been that interested in it, and because of my natural laziness I find it unlikely that I can ever make myself sign up for some larp.