Zombies have become George Romero's "brand" - as the creepy undead is what he's best known for.
Unfortunately, when a director get pigeonholed, it's really tough for them to counter pre-conceived attitudes in Hollywood. This is especially true for horror directors, who often want to helm other types of films.
All too frequently, however, the powers that be think horror is all they are capable of, or believe audiences are only interested in them directing "scary" films.
Knightriders was Romero's follow up to Dawn of the Dead, which never found an audience, although it was critically acclaimed. (Romero usually had the critics on his side with most of his movies, especially with Dawn and Martin, one of his most personal films that was similarly hailed by fans and critics, but failed to win mainstream popularity).
Knightriders was about a traveling troupe of bikers who put on renaissance fairs. Their leader, played by Ed Harris, tries to live by the code of the knights of the round table, refusing to sell out his principals. (When he says he's "fighting the dragon," it's a euphemism for corporate America).
Originally, Romero wanted to make a realistic movie about the legend of King Arthur, much like John Boorman did with Excalibur. He pitched it to the low budget indie company AIP, who wasn't interested, but in the low budget drive-in vein, he joked if he put the knights on motorcycles, maybe then they'd consider the idea. I guess both parties figured it actually wasn't such a bad idea after all.
AIP wanted to make the film like Death Race 2000, which Romero wasn't interested in, and he felt the marketing of the film, which looked similar to Rollerball, may have also cost the film. With Ed Harris dressed in armor sitting on a bike, people couldn't figure out what the movie was all about, especially considering Romero was coming off a big zombie film.
By this time, sword and sorcery was big at the movies with titles like Excalibur and Conan, but Knightriders never found an audience. IMHO, this was a real shame, because Knightriders was a terrific movie that proved that Romero could do more than just Dead movies.
Although it was an epic story, nearly two and a half hours long, like Martin, Knightriders is one of Romero's most personal films. Paul R. Gagne, author of the Romero biography The Zombies That Ate Pittsburgh, wrote, "Knightriders is regarded by many as Romero's masterpiece, a heartfelt, virtuoso display of his range and depth as an artist."
And during a Q&A at a recent revival screening of Knightriders, Ed Harris recalled, "That was a pretty good little movie."