Phantom Hourglass, Spirit Tracks, or Adventure of Link. It's really hard to choose. Adventure of Link was just a horrible game because I didn't like the style of it at all. It was more of an experimental thing, but it's still a horrible game. The difficulty isn't what bothers me the most, but insane hard games are also annoying. The game is just horrible in itself, in my personal opinion. I've played and beaten it just to say that I've done it, but I didn't enjoy it near as much as every other Zelda game.
As for Phantom Hourglass, I found that game extremely boring. It was one of the few Zelda games that I thought I might not be able to play to the finish because I was so bored with it. For one, I don't like the way they made the DS games at all. The central dungeon ruined the game for the most part. Central dungeons are a horrible idea. People have tried to tell me differently, but I always come to the conclusion that they're no good and there are much better options. The sailing was horrible and the game was incredibly easy.
Spirit Tracks is mainly the same deal as Phantom Hourglass, except it was a lot more boring. They tried to make the train more interesting by adding enemies everywhere and putting in rabbits, but that only made me angry. The enemies were incredibly easy and not at all exciting, so I only found that they greatly decreased the quality of the game. It didn't make the train rides any better, and they made sure that I couldn't just sit down and wait for the train to arrive at my destination, either. The story was also incredibly horrible in Spirit Tracks, which was even more disappointing. It was strong and excellent at the very beginning and end, but in the middle it just kind of died down.
