My grand vision for Spider-Man would've been like this.
Spidey 3 still has the Venom symbiote, Sandman, and Harry the Goblin in it. Except, Peter truly becomes evil with the suit on (no silly dancing and bitchslapping MJ, but he still fucks up Harry and gradually pushes MJ away), Dr. Conners has a bigger subplot with examining the symbiote (this is key for #4) and the audience actually knows about the sound wave bit. Gwen Stacy becomes a legit love interest and not a non-factor. Eddie Brock has the same role, but his humiliation and hatred are more explained. Dark Spidey battles Sandman at the end (who escapes), and in the tussle Police Captain Stacy (Gwen's father) is killed, Gwen blames the death on Spidey. The emotional climax of the movie is when Spidey rips off the the symbiote and merges with Eddie Brock, who then vanishes into the night. The ending scene at Captain Stacy's funeral is a parallel of the ending scene of Spidey 1, but instead MJ rejects Peter as he is about to propose, this leaves Peter feeling crushed and dejected. This coupled with his dark side experience leaves him unsure of his position as Spider-Man and most importantly as himself.
Spidey 4 deals with Peter's growing relationship with Gwen (who still resents Spidey for her father's death, maybe too similar to Harry?) while still trying to patch things up with MJ. Meanwhile, Venom is terrorizing the city posing as Spidey, damaging his reputation in the city, too. No matter how hard he tries, Venom always escapes in the end. Also, Roderick Kingsley is introduced as the new owner of Oscorp after has become a scarred recluse. Kingsley becomes obsessed with Norman Osborn and knows of his being the Green Goblin, and he later becomes the Hobgoblin (not in this movie however.) Dr. Conners has been experimenting with the Venom symbiote and discovers it's regenerative properties. After losing his arm in the war (maybe one of his arms has always been prosthetic???), he decides to test the regen stuff on himself after mixing symbiote DNA with reptiles, becoming The Lizard. Somewhere in here, Venom kills Gwen Stacy, almost shattering an already emotional wreck (Peter) to near breakdown. At this point, The Lizard is also terrorizing the city and has allied himself with Venom (better than the half-assed Sandman/Venom alliance, trust me). Like in Spidey 3, Peter asks Harry for help with Lizard and Venom. In the fight, Brock/Venom is killed and The Lizard reverts back to Dr. Conners after Peter cures him (but for controlled bursts like the comics.) Harry doesn't die, but he leaves the city, never to return. Kingsley finally discovers the secret to the Green Goblin and uses his criminal connections to call in 5 other criminals with intentions to form the Sinister Six. Somewhere in there he and MJ get back together and she accepts his proposal for marriage.
Spidey 5 is the last Spidey movie and deals with Peter finally maturing into his role as Spider-Man, marrying MJ, and facing his greatest challenge yet: The Sinister Six. This variant of the Six is Hobgoblin, Kraven the Hunter, Mysterio, Electro, The Vulture, and Sandman. They've all conspired to defeat Spidey once and for all. I really don't know how this ends, but every remaining subplot is wrapped up, Harry returns to take revenge on Kingsley/Hobgoblin, too. Spidey wins in the end, and Peter and MJ finally get married, la la la. Somehow it's the best concluding movie to a series ever.
Please Spidey fans, tell me what you think of that idea.