First generation, Red and Blue. Both belonged to my two elder brothers, who were kind enough to let me play when the other wasn't. And when my eldest brother got Yellow, he let me play that too! I never got my own Pokemon Gameboy game until Silver.
I played them all, owned them all, still have my Blue with legit Mew on it. And as of today, I have played every Pokemon game released to date. Can't wait to see what the future holds and what the future Generations will hold for us Pokefans and Pokemaniacs.
I started on my friend's Red version, then I got my own Red Version, followed by Blue, then Yellow, then another Yellow, Gold, Silver, Crystal, Sapphire, Ruby, another Ruby, Fire Red, Emerald, Pearl, Heart Gold & finally White.