First of all, Green Goblin couldn´t care less on what grounds he was establishing his partnership with Spidey. His basic proposal was "join me or I´ll kill you", so threatening the guy with his secret was far from below him.
It wasn´t the same method, since he was actually putting kryptonite INSIDE his body, making it much harder to remove and they were on a piece of land in the middle of nowhere and Superman, already horribly wounded, fell to the sea. At that point, from all he knew, Lois and Richard were dead. There was no one to rescue him. He had his vengeance by watching his henchmen beat the **** out of him and stabbing him with kryptonite.