The answer to this riddle is "nothing." Nothing is greater than God, and nothing is more evil than the devil. The poor have nothing, while the rich need nothing. Finally, if you eat nothing, you will die.
This riddle is known as Paul Harvey's riddle. It gained popularity as the result of a rumored study performed by a man named Paul Harvey. Harvey's seemingly nonexistent study supposedly found that only 17 percent of Stanford seniors had gotten this question right, compared to 80 percent of kindergarteners. In truth, there has been no evidence that such a study was ever performed.