The driving factor behind good design is organization. Consider a brochure: essentially it presents a pile of information in a relatively attractive way, rather than as just a big chunk of text. Informational graphics such as the ones in the NY Times or medical charts persent a lot of information in a very small space. A good graphic design leads a viewer's eye around a page from item to item in order to tell a story. When it's done right, as in the works of Milton Glaser, for example, the results can be attractive and compelling as well as informative.