I don't remember when I started liking Pokemon. It seemed like it was always there...
But I remember I started playing during the Generation II days. However, my first game was a Gen I game, and I didn't get a Gen II game until 3 months before the release of Ruby/Sapphire. So, physically, I've been playing since the Gen II days, but technically I've been playing since the Gen I days. If that makes sense.