That’s a difficult one! The DNA from a single human cell would be about 2 metres long if all of it was layed end to end. A good measure of how much genetic information different species have is by measuring the size of their genome. That’s DNA for most creatures, all the genetic information. Genome size is measured in base pairs and the biggest according to wikipedia (http://en.wikipedia.org/wiki/Genome ) that we know of right now is for an amoeba (a single cell lifeform), 670,000,000,000 base pairs. Humans have around 3,200,000,000
Scientists are still working to sequence the DNA of other animals so it may be some time before we know the answer to this question.