Which sentence states a fact?
Wicked starred Kristin Chenoweth and Idina Menzel when it opened on Broadway on October 30, 2003. Based on a novel by Gregory Maguire, the musical Wicked is the most entertaining show you will find, on or off Broadway.
A fact is something that can be proved by research or observation.
Napoleon Bonaparte was shorter than King Louis XVI.
The statement above is a fact. The statement can be proved by researching the height of each man and comparing them.
An opinion is something that a person believes, thinks, or feels. An opinion cannot be proved.
Napoleon Bonaparte was a better leader than King Louis XVI.
The statement above is an opinion. People can have different ideas about what makes someone a "better" leader, so the statement cannot be proved.
The first sentence states a fact.
Wicked starred Kristin Chenoweth and Idina Menzel when it opened on Broadway on October 30, 2003.
It can be proved by reading a review of Wicked from the day after it first opened.
The second sentence states an opinion.
Based on a novel by Gregory Maguire, the musical Wicked is the most entertaining show you will find, on or off Broadway.
The most shows what a person believes, thinks, or feels. Another person might have a different opinion about whether one can find a more entertaining show.