20 Essential Comic Issues You Must Read Before You Die
1. Amazing Spider-Man #121
There are very few comics that can claim to have altered the entire comics industry, but Amazing Spider-Man #121 did just that.
The death of Gwen Stacy was a radical idea at the time. It birthed the idea that important characters weren't necessarily safe from death and that a superhero could even fail to save them.
This change in attitude marked the end of the silly and campy stories of the Silver Age of comics and a shift towards the darker and more serious stories of the Bronze Age.
Basically, The Night Gwen Stacy Died is the reason there isn't a Lion-Superman v. Bat-Baby movie.