The line work is great. I think the character work is really good. The problem is that it is so busy and flat that is loses focus. My eye is not drawn in well to the image. I don't see what the focal point should be. I am not sure if its the composition, or if its the inking and coloring makes it hard to distinguish shapes. Either way it fails to draw the eye in well to Link/Zelda, which I assume is what you want the viewer to focus on.
I'd suggest more contrast and trying out different reds to get more separation, give it some depth. Maybe make it so Link/Zelda appear more in the foreground, and the various monsters/castle appear behind. Or move them up higher in the composition.
Or maybe make it landscape instead of portrait. Because the bottom 40% works really well on its own: