The Green Goblin taunts Spider-Man by saying that, "In spite of everything you've done for them, eventually they [the public] will hate you". This seems oddly specific. But it makes sense when one realizes that Norman is partially projecting his anger over his own board of directors wanting to oust him from the company which bears his name, in spite of Oscorp turning a profit.
The Green Goblin is later proven wrong, of course, during the bridge scene where bystanders on the bridge band together to help Spider-Man out.
The famed upside-down kiss was timed perfectly during both Peter and MJ's stories and plays with the First Kiss trope; both Peter and MJ have had it exceptionally rough the whole film and prior: Peter lost his uncle and has faced constant abuse as both himself and Spider-Man, MJ's been constantly marginalized, browbeaten and stifled and has been assaulted twice so far, plus her boyfriend treats her like a hot trophy and she's rejected at lots of auditions. Naturally, they were in desperate need of something good in their lives and the kiss came right when they were both at their lowest.
Mary Jane's taste in men seems to be terrible, considering she dates a guy for his car at the beginning of the movie and she later dates Harry, who is revealed to be condescending towards her. The only time she stands up to Flash is when he tries to punch Peter for accidentally spilling lunch on him and she calls out Harry for not defending his best friend. In contrast, she breaks up with Harry when he won't defend her against his father calling her a Gold Digger floozie. What happened in between? Peter kept providing emotional support and telling MJ You Are Better Than You Think You Are, and MJ realized that she did deserve better.
As several Youtube commenters have pointed out, there's hidden nuance in the boardroom scene. When Norman learns he's being outed from Oscorp, he goes through all five stages of grief. Denial, Anger, Bargaining, Depression-well, he never quite gets to Acceptance.
A combination with Harsher in Hindsight; the brief nightmare Jump Scare during Peter's stay at the hospital with Aunt May shows Green Goblin roaring at the screen, but far into the background you can see a second Green Goblin standing atop a balcony. At first this looks a bit like a goof, but the very previous scene shows Norman and Harry hugging it out, and come the Sequel Hook of Spider-Man 2, Harry gets poised to become the New Goblin of Spider-Man 3...perhaps this was a warning sign of there really being two Goblins.
Why does the Green Goblin want Spider-Man to join him so badly? He shares Norman's desire for a partner/protege. Just as Norman wants Peter to be his surrogate son, so too does the Goblin for Spider-Man.
As cool as the Expressive Mask from the comics would have been, it makes a lot more sense in context that the Goblin has what he does. Here, Norman isn't necessarily aiming specifically for a goblin appearance, just something monstrous and eerie— it's J. Jonah Jameson who gives him his name. The bulbous scalp of the helmet seems to be designed for aerodynamics, much like high-speed athletic helmets. With this in mind, the goblin-like ears and face were seemingly built off of this top piece rather than it serving as the "cap" of the mask like in the comics. Given that Norman probably had to build it himself in secret to avoid suspicion or outright exposure, where he would even get a Hollywood-quality prosthetic mask without someone snitching on him later would be a valid question.
The infamous "I had to beat an old lady with a stick to get this" line, while clearly intended as a joke, makes sense when you remember what Goblin's disguise was in the burning building one scene earlier.
When Green Goblin lures Spider-Man back into the burning building by pretending to be an old woman screaming for help, the bystanders who pointed it out to him never found out that it was just a trick. If they saw him swing out of the building empty-handed, they may have thought Spidey just left a woman to die...or that he failed to save her and got badly injured.
