Which sentence states a fact?

 - Thomas Edison's inventions are more interesting than Nikola Tesla's.
 - Thomas Edison invented the phonograph.
The second sentence states a fact.
Thomas Edison invented the phonograph.
It can be proved by reading a biography of Thomas Edison.
The first sentence states an opinion.
Thomas Edison's inventions are more interesting than Nikola Tesla's.
More interesting shows what a person believes, thinks, or feels. Another person might have a different opinion about what makes something interesting.