I'd go with Yu-Gi-Oh! The Falsebound Kingdom for the GameCube. Buuuut maybe that's just because I was 12 at the time. I remember it being a weird mix of real time strategy and RPG elements that came together to be really fun. AND IT CAME WITH PHYSICAL YU-GI-OH! CARDS! Looking at reviews now, it looks like I might be the only one who liked it.