George Stacy is the father of Peter Parker's love interest Gwendolyn Stacy. He was retired from the New York Police Department and was well respected by his fellow officers. He was eventually brought out of retirement to serve in the retrieval of the Nullifier device. George liked Peter Parker and very much approved of his relationship with his daughter. He was also a strong proponent of Spider-Man, even going as far to try and create a stronger and more positive public opinion of him. Eventually George put together that Peter Parker and Spider-Man were one in the same.
George Stacy's first appearance was in "The Amazing Spider Man" # 56 and he went on to play a role in over 180 issues. In issue #87 Peter accidentally reveals to Captain Stacy that he is indeed Spider-Man. He sets up a ruse to try and prove otherwise but it doesn't work. In issue #90 Spider-Man engages in a rooftop battle with Doctor Octopus. As the fight intensifies, a crowd including George Stacy gather on the streets below to observe the action. Chunks of the building begin to fall from the rooftop. As the crowd scatters a child is left in harm's way. General Stacy lunges to shelter the child from the concrete debris but in doing so loses his life. As Spider-Man approaches him George's final words confirm his knowledge of Spidey's identity and his approval of Peter's relationship with Gwen. He says "Be good to her, son. Be good to her. She loves you very much."
George Stacy (written as John Stacy here) also appears in the Ultimate Universe and is quite different than in Marvel's main continuity. He's considerably younger and isn't a big fan of Spider-Man. He is eventually killed when trying to save a child from a bomb thrown by the Chameleon who is disguised as Spider-Man.
The Amazing Spider-Man (2012)
In the movie version of the comic series, George Stacy is portrayed by actor Denis Leary. Slight alterations were made to the comic book character to fit a movie version of him. One of these alterations is that Gearge Stacy was Anti-Spiderman. He did not agree that Spider Man was a hero and believed that Spider Man was merely a boy causing ruckus. Captain Stacy is skeptical of Peter and they are shown arguing over Spider Man's intentions over dinner at the Stacy household. He is portrayed in the movie to not approve of the relationship between his daughter and Peter. In the movie, the Captain assists Peter in defeating the Lizard. He does so by using a weapon of some sort to freeze the Lizard so Peter could quickly release the Anti- Venom. In the movie, instead of his final words being, "Be good to her, son. Be good to her. She loves you very much," like in the comic book series, his last words were spent asking Peter Parker to leave Gwen out of his future endeavors. He didn't want Gwen to be hurt by the multitude of enemies Peter would make as Spider Man in the future.