It's been awhile since I've seen 3, but let me try to defend it anyway.
![Wink ;)](./images/smilies/wink.gif)
As a disclaimer, I have no such thing as a character or comic book bias. I appreciate film within its own respective medium, regardless of whether or not it's an adaptation. The stories that great movies tell are stories that can ONLY be communicated appropriately through film, and a movie that tries way too hard to be an 'accurate' adaptation of a book or a musical ends up falling short (one of the main reasons I had misgivings about both The Hunger Games and Les Miserables).
Sam Raimi knows how to do this. He understands his medium. Granted, Spiderman 3 was not an excellent film by any standard. Most of the blame for that goes to the Studio pressure that forced him to give in and add all those extra characters. But given what he had to work with, the man did a fine job. The reason the trilogy as a whole was so successful (most notably Spiderman 2) was because Raimi chose to focus our attention on the Hero's internal journey. Much attention is given to the small things. Peter's awkward, out-of-place personality. His innocent love interest in Mary Jane and his first real conversations over the fence with her. His unique relationships with his Aunt, and with his Uncle. Other superhero films give us the character's backstory too, but most of the time the character's relationships are only important in so far as they provide a convenient setup to the 'real' story, which involves superpowers and bad guys and special effects. In the Spiderman trilogy, the opposite is true. Yes, Peter Parker becomes Spiderman, but that isn't the real story. The real story is who he is becoming as a person; who is becoming to the people in his life. The fact that he also has superpowers and has to fight villains is only a plot devise that helps us understand his story a little better.
At the end of the first Spiderman, Peter isn't dwelling in the accomplishment of having defeated the villain. There are no victorious moments with cheering crowds and honorary awards. Those may come later. But for now, he stands in a graveyard, reflecting on the decisions he made. Mary Jane finally confesses her love to him, which is the moment we've been anxiously hoping for. But rather than 'getting the girl' in the end, he realizes something of greater importance. The theme of responsibility is potent. His role as Spiderman isn't a novelty or a convenience, it's a curse as well as a blessing. Turning his back on the girl he's always wanted, he chooses to embrace the role of great responsibility.
The second Spiderman takes this theme even further. Trying to live two lives isn't working out, and on top of that, his powers are waning. Everything seems to be going wrong. Finally, in an act of desperate desire for a comfortable life, he discards his role of responsibility and settles back to normality. At first, this seems to be the solution. But his decision starts to weigh heavily on him. It's not until he again sacrifices his love for the girl that everything falls into place. His powers return. He's able to defeat the villain, rescue the girl, and his identity is even revealed. It's the 'big moment' we saw at the end of the first flick. Yet as they lay together on the massive spiderweb, Peter knows that she still isn't his to have. So in another act of responsibility, he lowers her down to her fiance on a web and returns to his apartment. The final scene has Peter standing alone, with a face of sacrificial determination. Yet at his door, Mary Jane stands in a white dress, giving herself to him. In the end, his faith is rewarded.
Everything culminates in Spiderman 3. Peter's rivalry with Harry takes a genuinely thought-provoking twist, and ends with emotional resolve. The black goo from space offers a scenario that allows Peter to explore the 'dark' side of his gift. Eddy Brock is a genuinely believable character who only wants what Peter wanted back in the first movie. In many ways, he's an excellent mirror of Peter's personality, and because of that he's the perfect rival. Even 'Emo Peter' is totally brilliant. Remember, Peter was a total nerd at the beginning. He's grown up since then, but under the symbiote's control, the arrogant, prideful dork inside of him comes to the foreground. It's ridiculous, but that's because it's supposed to be.
Once Peter realizes that he's hurting the people around him, and failing his Spiderman responsibility as a result, he heads over to the church in order to be cleansed. Brock also heads to the church, but for a very different reason. His hatred makes him the perfect catalyst for the black substance that Peter is choosing to reject. Say what you want about the 'misuse' of the Venom character, but in the context of Sam Raimi's Spiderman 3, Brock is the perfect villain. He's the dark reflection of Peter's potential. Rather than fighting the temptation of power, he succumbed to its potency, and it cost him his life.
Sandman was, in my opinion, the only real weak point. His plot was just a little too far separated from the rest of the story. It did bring home the theme of forgiveness in relation to Peter's uncle, though, so that's a fair resolve. Again, I'm super impressed with the way Raimi weaved this seemingly out-of-place character in with the rest of the plot.
All the while, May Jane has been pushed away by Peter as a consequence of his temporary duet with darkness. Not all hurts heal right away (plus there's not enough run-time left), yet we're still given a final, wordless embrace. Forgiveness will win out in the end, just as it freed the Sandman from his painful regret. There is no final voice-over this time, because everything has already been said. Peter Parker's story is resolved. I, for one, I am glad we never saw any further sequels with these characters.
Oh, and the new Spiderman reboot was awful. I could easily write an essay just as long as this as to why it was a bad film on almost every level. >_>