I, like many others, fall into this pit. Let me explain the two reasons why this happens:
1) I get huge expectations for every new Zelda game. I expect it to bring back the feelings of adventure and love that I felt from the older titles. What I conjure in my head is above what the new Zelda delivers (perhaps it is impossible to reach what I desire) and so I hate the game when it is released. It will likely slowly grow on me over the years as my expectations have withered and i start to learn to appreciate it for what it is.
2) Every new Zelda game somehow takes what I disliked and focus MORE on it, or making the overall Zelda experience worse for me. This, in turn, makes the previous title look a lot better. A mediocre-looking female all of a sudden looks hot once a very similar, yet ugly girl stands next to her (real studies have been done on this). The new Zeldas continue to get worse and continue to make the previous ones look better.
It's sort of a combination of those two for me. This is partly why I went into Skyward Sword not knowing ANYTHING before-hand, so I couldn't raise expectations. I was still really bored with it, however, and only really enjoyed the last half-hour of it. But damn that last half hour was awesome.
