George O'Hanlon, who became the voice of the cartoon world's man of the future, George Jetson, after unsuccessfully auditioning for the role of Fred Flintstone, has died in Los Angeles after a stroke. He was 76. O'Hanlon had just finished recording his role as George in "Jetsons: The Movie," a full-length cartoon from Universal Pictures and Hanna-Barbera scheduled for release this fall. "George loved doing the Jetsons. He just sounded great in our latest sessions," Hanna-Barbera President Joe Barbera said. "I know he would feel very proud of his work in the movie."