Gwen Stacy dies over 100 issues into the comic, not issue 3. Bruce's parents dying shows is a part of why Batman is the way he is but that actual event doesn't weigh on the audience because we don't care about his parents and were never given a reason to. If Peter walks away from MJ in movie 3 or 4 then it would mean more because we saw their relationship grow over time, you don't want anything bad to happen to Ned because we've seen him in 3 movies now. Earn the emotion, don't just tell me I'm supposed to care.
Lets boil this down to its simplest terms. Bruce Wayne's parents dying is a story beat, it gives part of his back story but it doesnt have an impact on the audience because we have no relationship with them. Joker killing Robin is an emotion beat as we have a significant relationship with Batman, Robin, and Joker at that point in time. Emotion beats are what i want Marvel to focus on, like when everyone assumed Pepper and Tony would end their stories in a wedding as that happy ending felt pretty well earned so when it ended in a funeral instead it was like wow, you really felt it.
The loss of Gwen Stacey is compounded by his loss of Uncle Ben. Peter had already loss so much and to lose the love of his life re-opens the wound that was left their by the loss of uncle Ben. It reinforces what it means to be Spider-Man and the cost of being him and the audience empathizes even more for him because we know how much he has already lost. Over the entire first movie we see peter pine for mj only to realize that to be Spider-Man he can’t have her so he leaves her. His experience with green goblin had taught him how dangerous a sustained relationship with him will be.
Does this peter learn that after his encounter with the vulture even after being told by him he would kill his entire family? Nope, not at all no growth from the first movie to the second movie at all. This protege surrogant son thing that they got during the civil war era of marvel was irritating in the books and it is more irritating in the movie.
Everything is a story beat, batman’s Parents death even if we don’t know his parents makes you empathize with him because watching an eight year old boy watch his parents get gun down in front of him is heart wrenching. We don’t need to know the eight year old or parents because we know no child should ever experience that. It is why Bruce and dikk stand out in the bay family.
Through Bruce and the longing for his parents do we form a relationship with them. When Bruce gets that letter from his dad in the comics and asks him not to be Batman you feel it because we know how much his dad meant to him. We don’t know thomas that well or the flying graysons but we know Bruce and dikk and when you see dikk standing in the circus ring looking up you feel it because you know what he loss.
No one liked Jason Todd that is why people voted for him to die. It is not the connection to Jason that causes the feelings it is bruce’s Reaction to it. Bruce finally opening up to dikk and saying he missed him and replaced him with Jason because of his lack of emotional availability because of the trauma of watching his parents death. Without put those moments you get nothing. Peter and Bruce without those traumas you don’t get those characters because it informs everything about them.
And let’s not forget the death of captain Stacey earlier where he asks him to be good to his daughter before he dies.