Here, I'll start. When I was 8 years old, my parents went to a dinner party and plonked me down in front of the host's computer so I'd stay out of their way. The game they booted up to keep me occupied was Space Quest II. Little did they know what impact that would have on me...
Technically Leisure Suit Larry was the first adventure game I played when I was 3, but I was just walking back and forth in front of the bar because I didn't know what a text parser was. I think the game that actually got me into the genre was Myst, as divisive as it may be. I loved playing it with my family and exploring that world.