Well, I think I was a fan at first contact.
It was back in 2001, I think, shortly after my 5th birthday. I just remember that I got Turaga Onewa and immediately built him up when I got home. He was perhaps also the last Lego set, my father helped me building. Before we went on holiday that year, I got Turaga Vakama, too. After the holidays my collection had increased by Turaga Whenua, and Toas Onua and Tahu. By christmas I was able to name all Toa, Turaga and Rahi, as well as their masks and their powers.
I watched my father playing the Mata Nui Online Game (I couldn't understand English then) and when I played it myself for the first time this year I even remembered some stuff from back then!
In kindergarten and school I practically forced Bionicle on my pals, going so far as to have some kind of real enactment role play going on for the better part of eight years. (It featured some kind of Kikanalo-god who had to fight against pretty much every evil guy ever coming up in Bionicle as well as the four horsemen of the apocalypse, Hades, god of the underworld, a Dark Kikanalo, gigantic dragons and stuff ... man, those were good times ...)
I sure was lucky to grow up with Bionicle G1 from the beginning to the end.