There be spoilers ahead, so if you haven't seen Amazing Spider-Man 2, consider yourself warned. Also included are spoilers for a 31 year old comic, but if you haven't read it by now, I don't really care about spoiling you.
As Zack Snyder proved with Watchmen, it's easy for adaptations of iconic comics can easily fall flat. How do you maintain the power of the most momentous events in comic history when they're so well known?
Bryan Singer made huge changes to the death of Jean Grey (and then Brett Ratner made even more changes to her second death). Christopher Nolan still broke Batman's back over Bane's knee, but it happens so fast, it doesn't have quite the impact of the comics full page splash. They're good, but none of them match the power of the original material. And none of those have been as iconic or enduring as the events Marc Webb and crew had to tackle for this film.
The death of Gwen Stacy in Amazing Spider-Man #121 is one of the most tragic events in comic history. But that comic is over 30 years old. Andrew Garfield and Emma Stone hadn't been born when it happened. So why am I still teary-eyed Gwen Stacy die onscreen two hours later? A lot of that is on Garfield and Stone. The two have fantastic chemistry, and it makes it hurt even more to know we won't get to see it again (in this context, at least).
The other thing that really hammers it home is the pacing of the scene. Webb draws it out, leaving us breathlessly hanging on waiting to for the other shoe to drop. Gwen hangs precariously for so long before falling, and spends even longer on the fall itself, making her last moments brutally linger. And then she hits the ground so suddenly that even with all that build-up, it's still a shock.
My hat is off to the cast and crew of Amazing Spider-Man 2. That was a remarkable bit of filmmaking.