I have been to 5 of 10:
Prague's Old Town, Czech Republic
Eiffel Tower, France
Grand Canyon, USA
Pyramids, Egypt
Machu Picchu, Peru

and really only Prague was what I would consider crowded. But I prefer to travel in the spring and fall, so perhaps that helps. The Pyramids were next to empty when I visited (and this was several years ago, before the recent political turmoil). Have to agree with the touts in the Cairo area - by far the worst I have experienced anywhere in my limited travels.