Who am I? You sure you want to know? The story of my life is not for the faint of heart. If somebody said it was a happy little tale... if somebody told you I was just your average ordinary guy, not a care in the world... somebody lied.
Spider-Man: Peter Parker is bitten by a spider and finds himself with unique spider-like powers. He learns that with his newfound strength he has a responsibility to help people in trouble as Spider-Man after his Uncle Ben is killed by a mugger he could have stopped. Meanwhile, billionaire businessman Norman Osborn tests a Super Serum formula on himself to keep the project alive, turning him into the insane Green Goblin, who sets his sights on Spider-Man.
Spider-Man 3: With his personal and super hero life worked out, Peter is enjoying a high point. Things change as he has to deal with the fallout of the Green Goblin story and his own desire for revenge when a man connected to Uncle Ben's murder, Flint Marko, escapes prison, and is mutated into the powerful Sandman. Adding to this is a rival chasing his heels named Eddie Brock, and a mysterious black goo that attaches itself to Peter, heightening his aggression.
Adaptation Distillation: Classic moments, images and arcs from 40+ years of Spider-Man stories are squashed down to their best bits to fuel the films, though the 60s and early 70s are clearly the main inspiration.
Adaptational Heroism: A mild example. With the exception of Venom, almost all villains are more sympathetic compared their comic book counterparts.
Stan Lee protects a little girl in the havoc created by the Green Goblin in the first film. In the second, he pulls a woman out of the way of falling debris while Spider-Man fights Doc Ock; "Look out!" is his only line. In the third, he has a much more substantial cameo as a man who talks to Peter on the street. "Y'know, I guess it's true what they say: one person really can make a difference. 'Nuff said."
Bruce Campbell appears once in every film as someone who actually helps develop Peter's plot in some small way. In the first movie, he plays the ring announcer who introduces Peter as Spider-Man instead of "The Human Spider" as Peter originally wanted. In #2, he plays an usher at the theater who refuses to let Peter in because the doors have already been closed. Finally in #3, he is a french Maître d' at a restaurant who gladly helps Peter with his plans to propose to Mary Jane (though it doesn't exactly work out). It's also deliberately ambiguous as to whether he's supposed to be playing three different characters, or one character who delights in holding down different jobs with different personas.
In the licensed games based on the films, Bruce also serves as the Lemony Narrator who walks you through tutorials. Though he doesn't seem very interested in it; at one point, he leaves to grab a sandwich.
Civvie Spandex: Used in the second and third films. Dr. Octopus wears a trenchcoat and a suit. The Sandman, meanwhile, sticks to a pair of khakis and a green striped shirt while in Flint Marko form.
Clothes Make the Maniac: The alien symbiote in the third movie, and depending on your definition of "clothes," Doc Ock's tentacles in the second movie.
The Coconut Effect: The movies start off highlighting Spidey's use of Spider-Sense in slow-motion, but as the films progress, the Spider-Sense is more often implied that explicitly depicted, usually in the form of whiplash-quick reflexes and/or Off Hand Backhands. Notably, the third movie never highlighted it at all, with Spider-Man's reflexes and Spider-Sense all rendered in real-time.
Mary Jane has some traces of Gwen Stacy, flat-out stated by Word of God to be the case. Her lively but pained character is based on comics MJ, but her "girl next door" exterior is comics Gwen. Mary Jane also has a strong basis in Liz Allan. Like Allan, MJ in the movies is a classmate and longtime crush of Peter's who is much higher on the social latter and dates Flash Thompson (although MJ did briefly date Flash as well, it didn't last long). The actual similarities MJ has with her comics counterpart are her red hair, her being Peter's neighbor, her coming from an abusive household, her brief relationship with Harry Osborn, her vivaciousness masking her insecurity and pain, and her aspirations to be an actress.
On the flip side, Gwen in Spider-Man 3 has the bubbly sweetness of comics Gwen but the flirty, good time loving exterior of comics MJ! She also takes Mary-Jane's original role as the "other potential love interest:
Deadly Dodging: Done by Spider-Man in a lot of fights, most notably the Green Goblin's death.
Death by Secret Identity: Green Goblin is impaled soon after he discovers Peter's secret. In the second film, a big part of the movie marketing was that Harry would learn Peter's secret, but Harry's death wouldn't come until he made the full transition to baddie in the third movie. Peter also reveals his identity to Doc Ock. In the final movie, this works against Eddie Brock/Venom, but actually leads to the redemption of the Sandman. If this trope is truly in full swing, then all those people on the subway in Spider-Man 2 better look both ways before crossing the street...
Development Gag: The second film has a couple of playful jabs at Tobey Maguire's back problems, which nearly forced him to drop out. This includes the "I'm back, I'm back! ...My back, my back!" scene, and a Freeze-Frame Bonus Bugle headline claiming link between back pain and brain shrinkage.
Distressed Damsel: Mary Jane gets kidnapped by the villain in the climax of all three movies. She's also in distress twice before the climax of the first.
Once his Sanity Slippage starts, the Green Goblin chews the scenery in every scene he's in.
Eddie Brock after bonding with the Venom symbiote.
"Ooh, my Spider Sense is tingling, if you get what I talking about. Tiger."
Female Gaze: Well, of course. We're talking about a muscular young dude who wears a skintight outfit and is unbelievable agile.
Foreshadowing: In the first film Harry Osborn says of his father "If I'm lucky I'll be half the man he was". Come the third movie, we find out what exactly is meant by this. There are other foreshadowing moments involving Harry, such as the green bowtie he wears during the wedding scene in 2, and "They're my best friends ... I'd give my life for them".
Ivy League: Although Peter Parker attends the fictional Empire State University (modeled after New York University) in the comics, the Raimi films make him a student at Columbia.
Jerk with a Heart of Gold/Even A Jerk Has Standards: J. Jonah Jameson, the man who has no problem defaming Spider-Man for the sake of eye-catching headlines, lies to the face of the Green Goblin so as to protect Peter. The novelization looks deeper into his motives: Jameson always protects his sources, and has gone to jail twice for doing so in the past. In the third movie, he's furious that Eddie Brock gave him fake photographs of Spiderman, commenting that "We haven't printed a retraction in twenty years!" Not only did he fire Brock, but additionally had him shamed on the front page alongside the retraction.
Large Ham: All the villains but Sandman. Also, J. Jonah Jameson and Bruce Campbell's cameo appearances.
Special mention has to go to Willem Dafoe as the Green Goblin. When he is fighting Peter, he is having the time of his life, complete with evil cackles and poor one-liners.
Evil Is Hammy: In addition to the villains, Maguire was having FAR too much fun being Emo-Jerkass-Peter in the middle of the third film.
Lost in Imitation: A LOT of things from the movies were taken from the 90's cartoon series and not the comic books. Green Goblin being a split personality of Norman's developed from the Goblin formula and Norman talking to him was from the cartoon. The plot point of the Green Goblin going after people who wronged Norman Osborn was from the cartoon, Mary Jane being a replacement for Gwen on the iconic bridge scene was from the cartoon,Otto Octavius being someone Peter personally knew was from the cartoon, the symbiote augmenting Peter's powers and creating a dark side was from the cartoon, Eddie Brock working at the Daily Bugle as a rival photographer and not as a journalist somewhere else and his prior relationship to Peter was from the cartoon
Made of Iron: Spidey is a given; his powers allow him to shrug off huge amounts of punishment. But especially notable is Ock in the second film. He's an out-of-shape scientist who shouldn't be standing after one of the super-strong Spider-Man's punches. Even if Spidey pulls his punches, Ock takes a web-slung bag of coins to the face at one point without a mark to show for it, and also keeps fighting after being slammed through the floor when Spidey catapults himself from the roof.
Plucky Comic Relief: J. Jonah Jameson and his assistant Hoffman. Also Peter's landlord and his daughter.
Pragmatic Adaptation: Various elements of the Spider-Man mythology are altered to make a more straightforward narrative. The power-giving spider was genetically altered rather than randomly irradiated, his web slinging was made into part of his mutation rather than being an advanced mechanical device created by a teenager. Spidey's habit of quipping during battle was simplified, usually one or two before and one or two after it's over, since it's difficult to use Talking Is a Free Action. For sheer longevity Mary Jane was the most well known love interest among casual fans, but incorporated the Girl Next Door qualities of Gwen Stacy to simplify their history (In the comics MJ showed Hidden Depths by grieving with Peter after Gwen's death, which is what brings them together).
Redemption Equals Death: The second and movie have Octavius and Harry realize their mistakes and ultimately sacrifice themselves to repair it, Octavius drowns the proto-star and Harry dies protecting Peter from a fatal strike from Venom.
Reflective Eyes: The posters themselves use this as a reflection of who the villain of the movie was going to be.
Running Gag: Jameson keeps yelling for "HOFFMAN!" who keeps appearing faster and faster as the movies progress, much to Jonah's confusion, eventually culminating in Jameson screaming his name while turning around, only to be face to face with Hoffman before he finished saying his name.
Snark Knight: While not making as many jokes as other versions of the character, he does make a few in each movie at his opponents' expense. One of the common criticisms of the trilogy is the lack of combat banter.
Spider-Sense: After the first movie it's just implied, but Spider-Man reacts far too quickly to not be in play.
Spontaneous Crowd Formation: In the first film, they help Spidey by throwing insults and rocks at the Green Goblin. The second film plays on this, by having the crowd stand up to Doctor Octopus, only for him to easily brush them aside, snatch the defeated Spidey and carry him off.
Starving Student: Peter Parker, particularly in the second movie which has him struggling through college without money and his superhero identity compounding his hardships.
Trailers Always Spoil: When you watch the trailer after watching the movie, it's impressive how much plot is given. The most egregious example has to be showing Harry pulling off Peter's mask in the second film.
Norman Osborn, before the "Goblin" takes him over completely. He might have been rough and far from a saint but his reaction to finding out he killed people was to be horrified. The way he's been treated seems rather unfair too: A major funder switches their funding to a clearly inferior solution because they personally dislike him and the board of directors fires him from the company he built to get more money.
Doc Ock, a patient teacher and loving husband who inadvertently caused the gruesome death of his wife when his experiment went horribly wrong. After crossing to the dark side for much of the movie, he chooses to sacrifice himself to save the city in the end.
And Eddie Brock: despite being The Sociopath and a slimeball, his downward spiral into madness that ends up consuming him when he bonds with the Symbiote is just sad. Also Sandman and Harry, who are on the Anti-Villain side of things. Really, the only villains without any tragedy to them are Dennis Carradine and the alien symbiote.