I think in general, the US does a great job with National Parks and Forests. Can't say I've been to one where I've been disappointed. Too bad the help gets paid squat.
That said, I've had a bit of bad luck in my travels. First time I was headed down to San Diego from SF, a big swath of the PCH was closed due to fires, including Big Sur. I have photos from Hearst Castle taken on a sunny day around noon that look like dusk.
When I finally got around to an AZ/NV/UT trip, it was right after 9/11 and Hoover Dam was essentially in lockdown. Traffic lines were well over a mile long and each car's underside was searched with mirrors and sniffed by dogs. Thankfully the Grand Canyon and Zion weren't issues.
Overall, I think I have to go with the Big Island. Hawai'i in general is just so different from the mainland culturally and geographically that it's pretty close to visiting another country. And while we loved Lanai (driving a Jeep through pineapple fields), Oahu (USS Arizona monument is right there with the Vietnam Veteran's Monument as most sobering and stirring), Maui (got married on a beach, took a ferry from Lanai to Maui with goats and chickens on board, almost third world-ish) but the Big Island packs a whole lot of stuff into a pretty small space - active volcanoes, rain forest, huge cattle ranches, incredible snorkeling... and where else to you get to play golf where the landscape includes lava rock?