My first game was AC. But besides that, Melee was the reason I got my GCN. I really wanted a PS2 first, which I have anyway so it doesnt matter much, and I was renewing my NP subscription and I got the Melee guide as my free gift and thats what made me want my GCN.
If I remember correctly, it came out at the same time as Mario Party. I looked at it, didn't fully understand it, then I rented it. It got to the top of my want list immediately. I was... 7 or 8 maybe?