It’s like comparing apples and oranges – a beautiful forest is not a desert, for example.
That being said, my personal favorite is Iguazu Falls in Brazil. 275 waterfalls, crashing down on the Brazil/Argentina border. The spray of water bellowing upward. The continual crashing sound in every direction. Nature’s power on full display.
I’ve been to Victoria Falls in Africa and Niagara Falls in New York – they don’t compare. There is only one Iguazu Falls.