I personally grew up in the middle of the desert (I posted this in the "where do you live thread"). So there wasn't really any forests or anything to go play in. And my parents/grandparents were already into technology and games (grandparents ran a movie&game store, mom was into computers). That's where my gaming habits started. I basically got all the left over stuff from my grandparents. This was back way before I could remember anything (like 2-3 years old). So I basically grew up along side video games.
So my child logic went something like: These games are awesome. They had to get here somehow. I wonder how they work... Then a lifelong study of video games and computers. Note, this was when I was like 5-7. So I really had no idea what I was getting into.
I basically loved everything about figuring out how games worked, and actually managed to reverse-engineer a password system (rudimentary) in one of the games. I learned my way around the internet and computers sometime around there. By middle school I was learning about the innards of computers and how to program. That's what several of my science projects were about.
From there, I just kind of honed in on programming. Fast forward to high school, and I see there's game design and game programming classes. One's supposed to be advanced, but since my family was already well known by the school for a while, I was able to join both.
I started taking CS classes in my community college the next year. From there I graduated highschool early and transferred to my current Uni, where I'm majoring in CS (actually Info&Comp Sci, but it's really the same thing). And I'm in the Game Development club at the school.
So it's all been a really natural progression for me. I've never really had to think about what I wanted to do. And it's not like it was a last minute decision either. It's really just provided me with something to research and learn about. So I did. I was lucky to have family members who were (at least somewhat) interested in computers and games. And they were all very supportive.
But yea, there's been times where I've been completely hooked on games for the worse (my horrible Ragnarok Online addiction that lasted 7 years or so). And my Mom totally yells at me for that. But we both know that it has lead into great things.
So really, what lead me into CS (and game development) was: a lack of a stimulating environment, a family focus on tech, grandparents running a game store, and a curiosity about my interests.