I deinfately nail down games that defined my personality. Perhaps, for my then tender age (11-12), I shouldn't have gotten a hand on Gabriel Knight: Sins of the Fathers, but I'm sure as hell happy I did. I have vague memories of other adventure-y games I played before, but it was this masterful gem that set in this joy of complex, intriguing, powerful storytelling, and for investigation and reasoning. It was the stepping stone into adventure games, so the whole Gabriel Knight series and Jane Jensen's fantastic writing, belding of mystery and fact completely set the tone for the kinds of stories I like. The same feeling came back with The Longest Journey and Grim Fandango. I can't settle for shoddy, mediocre characters and plots. However.....
Tomb Raider, the first one, also gave me this deeply ingrained desire to explore and uncover hidden mysteries. Again with mystery. I guess it all can be stripped that games (along with the tons of books I devoured in my young age reading) just defined this "I need to know what's behind all this mystery, and I'll search for the answer myself" drive that I think eventually led me to be a scientist. Also, it helped me understand that being alone isn't bad, and having to rely on wits and nimbleness to solve problems can be better than brute strength. There was this recent article on Rock, Paper, Shotgun's "Gaming made me" about Tomb Raider, and it felt very familiar.
If we're going by books, I think Michael Ende's "Momo" really moved me in this idea that even the smallest things are important, and everything you do with people matters. "Don't become a materialistic person and treasure your time" was my take away notion, which I've tried very hard to keep up, even with the weird habits my profession tends to impose on me. Like Susan, Alice in Wonderland also made me feel incredibly happy that I "got" all the wordplay and clever little language distorsion going on. I didn't know Phantom Tollbooth was a book. I only saw the movie adaptation and it was great.