Well for me its hard to say when I got the bug. I remember my cousins had a black and white box with knobs that they hooked up to the family TV. I'm thinking it was '76 or maybe '77. Yes, it was PONG. But I don't think that's when I got bit. Many of my neighbors had consoles (Atari 2600, Intellivision, and the C64 too) that I didn't have to ask my parents for one. I could just go to the house that had the system I wanted to play and get my Jones on.
But to say what game really got me started in PC gaming. I would claim: Tomb Raider. The game that sucked me in i.e. the biggest time-sink when it was released: Omikron The Nomad Soul. I never finished that one because the first time I played it I lost track of time and my GF asked me if I was going to eat dinner. I asked her what time it was and she said 10:30 pm. Wha?!?! Four HOURS after I stared playing. It was at least a month before I played it again.