Just to add my two bits of thoughs: I think that next Zelda has to think to the magic ocarina of time delivered. Not in terms of just game-mechanics, but also because of the cohesion provided by a well made storyline with charismatic characters. Cut-scenes, even if very limited by the space of cartridges, were simply, but so full of feelings. I mean: the scene where Saria left Link is very short, but its value exceed what could have been done adding mere words. Further, adding majora's mask depthness and darkness, you can reach a multi-leveled adventure game, whose main force will not be the trivial, annoying and unsatisfying -dungeon-boss-go to next dungeon-procedure, but a true adventure game, full of surprises, memorable scenes and desire to never stop playing.
In this sense, I believe that Okami accomplished quite a remarkable achievement. It lacked many things, but not a good, non-obvious storyline. I was never bored playing Okami. But I was often bored as hell with Twilight Princess.
That's the point I think. The most trivial, but at the same time less obvious to reach achievement of a game is to keep the player on the screen day and night until the end. And at the end, just let him desire to restart the game again. You can say then that this was a so-called masterpiece.