Good question! I should think you would want to primarily take fine arts, or art classes in drawing and painting, with emphasis on human figures and animals. I remember going to a video game show at the Smithsonian American Art Museum some years ago, and it was interesting to see the sketches for many of the video games, and they were pretty traditional; those artists had solid backgrounds in traditional drawing techniques. This goes without saying that computer graphics classes will also be important, and having traditional art skills will enhance your cg experiences.
However, I also think that having a few graphic design classes would also be a plus. In graphic design you really focus on composition (design) in using color, line, shape, form, light, and so on, along with text. Please remember that no matter how well you draw, or how wonderful your ideas are, it really won't matter if you don't have a solid composition to pull the viewer in.
Best wishes! Hope this helps.