A bit of 'food for thought'...
In Peter's Google+post about the wiki parks project, I asked if Upper/Lower Antelope and Slot Canyons in Arizona could be considered for the list. The problem - they are not managed by the National Park Service but rather by the Navajo Parks and Recreation Department, which is not associated with the NPS. They are located on the Navajo Nation's land so the tribe(s) have jurisdiction.
Peter stated naming the article 'Famous Parks' would be too broad and then would include areas such as Central Park in NYC. I agree. So, I guess my question is: Do the entries on the list, at least for the US, have to be part of the National Park Service? The US Federal Government recognizes 562 tribal governments, which gives the nine American Indian Nations control of their own lands - which include some very well-known parks that people think are part of the NPS.
Also, is it only parks that can be included? An example would be Mount Rushmore Memorial, which is managed by the NPS, yet has a 'park' surrounding it. It's just not called Mount Rushmore National Park.
Rocky Mountain National Park
Redwood National Park
Biscayne Reserve (underwater with reefs and on-land area)
In my opinion, and it wasn't intended to do so (I started the article), the article is ment to be much broader.
I am planning to make one for other countries as well, for example South Africa. There you have the national park organisation as well, but some 'famous' ones like Madikwe and Pilanes are not on that as well, and sometimes are rather called a reserve or something.
So it can certainly be much bigger, including the ones you mention and including monuments etc.
The US has 58 National Parks/Protected Areas under the NPS, so lots of choices. But, several Nations also have control over some spectacular places. Just 17 miles from Mount Rushmore is the Crazy Horse Memorial, located on Lakota Tribal (Sioux Nation) sacred land. Construction began in 1936 and is still on-going. (It's been the target of several controversial issues which have slowed it's creation.)
There are the Anasazi Indian ruins which are located around the four corners area of Utah, Colorado, New Mexico and Arizona. There even a plaque in the ground at the four corners spot. You can literally be in 4 states at once.
Three Samoan islands are protected so more diving opportunities, volcanos in Hawaii and Denali in Alaska. Even the Dry Tortugas off Key West are protected. Contains Fort Jefferson which is the largest masonry structure in the western hemisphere.
But, I digress...