The original, for good story (decent background story, great main plot, good pacing, memorable characters), good visuals (beautiful backgrounds, good character design, great animation) and good sounds (stupendous voice acting, PHENOMENAL soundtrack).
X, for a good story, the battle with the trio of sharpteeth, and Bron in general.
VIII, for pushing the visuals, a good story, and Mr Thicknose.
IX, for the liopleurodon and everything related to it, espescially the big scene in the lake.