How about we split it into a 2D and 3D category? My favorite 2D Metroid has to be Metroid Fusion for the GBA. It was pretty short but all the fights were very fun and I really liked the different suit designs. Fighting yourself at the end was pretty awesome too. My favorite 3D Metroid has to be the first Metroid Prime for the Gamecube mainly because I never got into the other ones. It was the first one and it was new and amazing. I've been meaning to play the other ones but I just haven't gotten around to it. What about you guys?