Are Hollywood Films Realistic?

When it comes to Hollywood movies I believe that they do not get all the facts right when they make a movie based on true events. I think that they do know exactly what happens in the true evens but they choose to tweak it so it can appeal more to the audience. I typically do research when i see that a movie is based on true events and sometimes find out that a lot of the stuff in the movies either didn't happen or they've changed it around.