Here in the US, we are blessed with a multitude of great national parks. But I wonder if any of us can name a favorite. I think I have narrowed mine down to just a few, almost all in the western US.
Among my favorites are Yosemite NP (here in my backyard), Bryce Canyon NP, Arches NP, Grand Canyon NP, Zion NP, and Glacier NP. Three of these are located in Utah, one of my favorite states to visit. Most of the parks I have visited are in the west, except for Everglades and Acadia.

Much of what you like about a national park is what you like to do. For me, it is mostly the sights, some hiking, cycling, and most importantly, the photographic opportunities. I try not to factor in the expense or difficulty to reach the park. Sunrise and sunset are also VERY important.
Perhaps nothing is more magnificent than seeing the Grand Canyon for the first time. We took the train from Williams on Christmas Day and ate the best burger ever at the El Tovar. Glacier is off by itself, with the Going to the Sun Road as the big attraction. Arches pairs well with Canyonlands when sandwiched around a few days in Moab. I also try to visit Monument Valley (hello Forrest!) when in Moab.
We have driven to Yosemite many times. Each trip seems a bit different, whether the season, or who we might take. Both of our dogs have visited Yosemite! But I have yet to go cycling in Yosemite Valley, maybe this year?

But my favorite trip is the Zion and Bryce Canyon trip. I usually start in Vegas and drive up to St. George. After a quick stop at Nielsen’s Frozen Custard, I drive up to Zion, and meander through the park at a leisurely pace. I tend to go slightly off season to avoid the crowds. But after a short 2-hour drive, Bryce Canyon is my personal crown jewel of national parks.
You might wonder why, perhaps the hoodoos, or the many trails that welcome hikers and mountain bikers? No, it is quite simple. The park changes dramatically between sunrise and sunset. I strongly suggest an all day visit to capture the park in every stage of light and dark. I usually make at least four visits per day to various places along the main canyon drive.
If you qualify, make sure you get the Lifetime pass.