The year Pokemon yellow came out, I was at my Grandmother's house for Christmas and I got Pokemon yellow for it. I can hardly remember many details aside from the pure joy of it. This was only the second Pokemon game I had played (the first was Red, and I can barely remember starting that), and I was a little kid thinking that it was going to be the best thing ever.
And in some ways it was.
On the other end of the spectrum, I remember that one day my parents had a friend over and they brought their kid, a guy around my age. I decided to let him start over my red version, but only temporarily because I still loved the Pokemon on my Red file (it was my first game, I might still have had my very first Pokemon on there). I didn't intend to save it though; we were just going to go through the beginning then turn it off when he went home. Then we had to go eat supper, and without thinking we saved the game so we could come back to it later. It wasn't until after we got back that I realized what I had done. I was so mad... I don't remember much of the details after that but the feeling of regret still lingers to this day.