Why is Metroid considered a part of some holy trinity? Shouldn't it be something more beloved like Mario Kart or Smash Bros.? If you take it from Nintendo's point of view, Metroid is a second tier series because it doesn't bring in much more than 2-3 million per title. That's why they have no problems releasing it in the same year as larger selling titles like Mario Galaxy 2 and a new Zelda.