While Green Goblin died at the end of Spider-Man in a manner similar to his first demise in the comics (being impaled by his own glider), that didn’t mark the end of Willem Dafoe’s time in the first Spider-Man film series.
Since Chris Cooper only briefly appeared as Norman in The Amazing Spider-Man 2, the same movie where Dane DeHaan’s Harry took on the Green Goblin mantle, Willem Dafoe is still the definitive cinematic version of Norman, and fortunately for the actor, he had a good time acting out the character.
He cameoed in Spider-Man 2 and Spider-Man 3 when Harry Osborn, who now knew that Peter Parker was Spider-Man, saw visions of his father that pushed him towards seeking vengeance against Peter for Norman’s death.