I think I was 8, on the last day of the school year we were all allowed to bring in Toys, about half the school brought in their Gameboy with a Pokemon game, I saw them all playing and having fun so I begged my parents for a green Gameboy colour, which I got about a week later. It was the year 2000 so I saw gold and silver at the shop, but I chose to buy the Yellow version.
Then I went to my granny's house and started playing immediately, before I left I was in the Pewter Gym, and because I had no idea how to play the game I took Brock on with Pikachu, Rattata, Pidgeotto, Metapod, Nidoran (m) and Nidoran (f) and somehow, I won. =]
I think I managed to get to Cinnabar island before I realized how to properly play Pokemon, so I changed Ratticate for Snorlax, Nidorina for Zapdos. (I kept Pikachu, Pidgeot, Butterfree and Nidoking)
Before I went on holiday the next year I was given Gold Version which blew my mind, the new Pokemon, the fact they could eat berries, the day and night modes, the improved graphics etc. For the first time I was given a choice of three Pokemon to start with, I went with Totodile. When I beat the elite four my team was Feraligtr, Sentret, Noctowl, Corsola, Sudowoodo and Ho-oh, but by the end of the game it was Ho-oh, Lugia, Zapdos, Mew, Mewtwo and an undefeated Snorlax. Not a very balanced team I know, but I was young and still under the impression that Legendaries defeat all other Pokemon. (And all mine were at Lv.100, which took ages, but was worth it)
I was really weird with my Gold version, my Pokedex was full, I had beat the Elite Four 251 times and the timer was saved at excatly 251 hours, in Red's space on Mt. Silver. I also formed the "Elite Four" at school with my friends, none of our challengers ever beat us, but to be fair we only had about five of them...
Wow, I wrote quite an essay, sorry about my stupidly long reply.