If you want to show a lot of data, spread it out onto multiple slides, with one key message per slide.
The slide shown above comes from a recent seminar. Too many bits of information on a single slide dilute the message. In addition, the slanted writing in the background also competes with the data for attention.
If you are not familiar with Garr Reynolds and his presentation zen blog/books, take a look at some of his great examples of having just one key message per slide. His books are listed in the right column with other reading suggestions.