Xenoblade is the exception, not the rule. After that game I'm not sure I can get through the many problems almost all other open world games have anymore. Even the Assassin's Creed games, which I love, were completely wasting my time until I got to the linear missions and the linear tomb areas were the best parts of the game. And Metroid shouldn't arbitrarily be turned into something it's not solely to appeal to what's cool. Metroid doesn't need this. Prime and Super Metroid are far more engrossing experiences than most open world games anyway, largely since they are brilliantly made worlds with great atmosphere but they also have really good linear and even non-linear level design. Metroid could use more non-linear parts again, but open world is not the answer.
And beyond all this, Zelda's the game that could use a huge open world. Or even Star Fox, like some PC-like space strategy epic or something, that would be awesome.