#19 Pokémon Crystal
Yes! This! I did almost everything that was possible to do in the second Pokémon adventure. Crystal being my version of choice because it was the latest game in the series released when I got my Game Boy Advance. Two whole set of worlds and gyms. The best secret boss fight ever. Super rare Pokémon of different colors. And you could play as a girl!
My first experience with Pokémon was playing on a game boy emulator and I was not that big of a fan. But since even the "cool" kids at school played and traded Pokémon I thought to give it a chance. Now I probably would recommend the Heart Gold and Soul Silver for anyone who wants to experience this game since the graphics of crystal are outdated and it includes some extra bells and whistles. But Crystal is for me such an iconic game from my childhood that I will not trade it for any newer and supposedly better version.