One message per slide, please
If you want to show a lot of data, spread it out onto multiple slides, with only 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. Can you tell in a few seconds what the charts show? 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 in the presentation below.
His books are good inspiration, and they have been translated into many languages.