I feel the races in Oot, MM, and WW complicated the series. I thought they held an ideal of simplicity and accessability. I didn't like all of the wierd species and hated the evolution which I try to just ignore. Too little time passed for such changes, too much time passed without technological progression to seem logical, and too much time passed between stories for the mythos to make much sense or for the gamer to feel connections. Its like the new trilogy of Star Wars and how it is becoming evidently sucky in comparison to the classic genre movies of yesteryear.
There have always been mystical races in the series, but they should remain consistent; and they shouldn't change the rules of the universe with each installment while not really changing anything about the adventure or story. Four Swords though actually changes the gameplay. All Zelda needs now is lots of AI in the computer controlled characters and emphasizing on a story that could be both simple and epic without interupting the flow of the game. There just hasn't been a real story in a Zelda game even though each story gets more complex they haven't created any story with the literary equivalent value to the value of the art and gameplay found in the games already.
I also believe that the first Zelda was the hardest in the series, WW is the easiest, and LttP is the bowl of grits that's just right.