Not sure when, but I was about 14, maybe a little older or younger who knows.. I'm 20 now.
It was halo 2, my brother was staying at my house and he ended up getting a live account on my xbox, and he always called me a flamer for not playing Halo, I was more into far cry, eventually I played as a guest on his account and everything changed from there, I LOVED halo 2 matchmaking, and i dropped all other games and just started playing halo, been in love ever since.