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...
I think the first point n' click adventure I played was Maniac Mansion (for the NES!) at a friend's house.
But really what got me into them was Monkey Island. I had an Amiga 500 and we got some games from a friend who had recently got a PC. among them were 4 (I think?) disks labelled "The Secret of Monkey Island", and - dammit Ron - I was immediately intrigued by The Secret.
Monkey 1 was one of very few games I bothered to actually come back to and eventually after many months complete by myself as a kid.