Final answer:
The highest grossing science-fiction film as of 2013 was 'Avatar', which had a worldwide box office gross of over $2.7 billion.
Step-by-step explanation:
The highest grossing science-fiction film as of 2013 was Avatar. Directed by James Cameron, Avatar was released in 2009 and had a worldwide box office gross of over $2.7 billion. It combines elements of science fiction with fantasy and adventure, and is known for its groundbreaking visual effects and immersive 3D experience.