It looks like there's another 7 Wonders List that's being formulated. Except this time, it's about the Seven Natural Wonders of the World. A pair of major waterfalls feature prominently among the finalists. They are Iguazu Falls and Angel Falls.
You can see the other natural wonders finalists by reading this article from the examiner.com.
It's also worth noting that the Milford Sound in New Zealand is in the other half of the finalists list.