So even in keeping such acclimation to the same idiom--i.e. not a Springsteen concert or Hamilton or the Cubs winning the World Series--you should only get one choice.
Fooey, I say.
Just within the vernacular of sights seen in traveling around the world, I've seen many astonishing things including the Pyramids of Giza, the Treasury at Petra, the Taj Mahal, the Sydney Opera House, the Sistine Chapel, the Eiffel Tower, Bryce Canyon and myriad more.
So is Machu Picchu the greatest thing I've ever seen?
Today, just hours removed from seeing it, yes it is. It was ever bit as breathtaking as I could've imagined.
If you can see the pictures I shared on Facebook, take a look. They're worth every word I will write here, and many more.
As for a paramount proclamation across time, place and different sorts of "sights," even within a travel realm, who knows, who cares?