Disneyland is so popular because people always feel the magic when they are inside the theme park. They can begin to feel like children again wherein they do not have to think about their problems and their responsibilities. Even if they need to spend a lot of money for the entrance, they still push through with it.
Some Disneyland Parks are so big that you cannot explore it in a day. You would need to stay a few days to explore all sections. Staying inside the park can be expensive though so some people opt to stay nearby so that they can go back. There are some passes that can be purchased specifically for that.