Those aren't quite right.
The word 'media' is plural. The singular form is 'medium'. But a movie is not a medium.
You might say,
Film is a popular medium. Movies are popular.
Apples are popular. The apple is a popular fruit.
Engineers are popular. Engineering is a popular occupation.
The rules are to do with 'number-agreement': An apple is... Apples are... But there are exceptions to the rules and the US and the UK differ in the way they observe the rules.
This post explains some exceptions to the rules.