Moviegoers love romance. So do movie studios.
Just look at the box office take last weekend. After weeks atop the box office mountain, it was weepie Dear John, a movie described as "corny, sappy" and a "far-fetched love story" that finally knocked Avatar off of its throne. Dear John earned $32 million to Avatar's $23 million.
So what happens when you combine a believable romance with the kind of fan-boy obsession heaped on Avatar? You get Hollywood's version of the perfect Valentine's Day present and the secret to creating the movie business' top-earning on-screen couples.
Peter Jackson did it with his Lord of the Rings trilogy. Yes the film was about Frodo's quest to throw the Ring into Mt. Doom. But the coupling of Viggo Mortensen and Liv Tyler convinced a lot of girlfriends to sit through more than nine hours of orcs and wizards and hobbits. With $2.9 billion in worldwide earnings, the Lord of the Rings trilogy puts Mortensen and Tyler at the top of our list of Hollywood's highest earning on-screen couples.
To compile our list we considered romantic parings that had appeared in at least two films together in the past 20 years. We ranked the pairs based on non-inflation adjusted worldwide box office grosses, as calculated by Box Office Mojo. Animated movies were not included.
Ranking second behind the hottest couple in Middle Earth is another non-traditional romance: Tobey Maguire and Kirsten Dunst from Sony's ( SNE - news - people ) Spider-Man trilogy. As Peter Parker and Mary Jane "MJ" Watson, they put heart into the $2.5 billion franchise. Their onscreen chemistry wasn't enough too keep the series rolling though. In January Sony announced it would reboot the Spider-Man franchise with a new director and new stars.
Ranking third: Leonardo DiCaprio and Kate Winslet. The couple has the advantage of appearing in the second-highest grossing film of all time, Titanic, which brought in $1.8 billion at the worldwide box office. They starred together again in the 2008 drama Revolutionary Road as a couple whose marriage goes under, earning $75 million at the worldwide box office.
Shia LaBeouf and Megan Fox rank fourth for the two Transformers movies. The chemistry between the two stars helped ground fans who might otherwise have been totally distracted by giant robot cars running around on screen. The two movies earned a total $1.5 billion at the worldwide box office.
But the multi-movie onslaught of Robert Pattinson and Kristen Stewart may prove the most powerful and profitable of all. With just two of the four expected Twilight films under their belts, their pairing raked in $1.1 billion at the box office. The third installment, Eclipse, hits theaters at the end of June.