Gwen is imprisoned at the clock tower. Green Goblin takes her to the sky and drops her down. Spidey comes and catches her and the both fall into the clock tower (Gwen is still alive.) Harry Osborn comes though the roof and fights Spidey, Spider-Man kicks him off his glider and Harry falls down Peter webs him realising he is still his childhood friend even for everything he has done.
Next Day: The night is over Norman Osborn takes the Oz formula and transforms into the Green Goblin (as his son didn't complete his set task, a proceeds to complete it himself.) Gwen and other New York citizens watch the bridge as a hint of green is spreading in the clouds, Gwen gets kidnapped by the Green Goblin. He takes her to the bridge, Peter realise something is wrong at the bridge and he swings though New York City to save Gwen and she meets her fate same way as the famous comic book "The Night Gwen Stacy Died."
Let me know your theories below.