What is it that has driven this franchise? Spiderman is the ultimate superhero, grounded by his own emotions. It isn't what takes place in the air as he swings into action, it's always been what happens between the action. That's where the heart and soul of the trilogy(so far) lies.
That being said, Spiderman 3 has proven to be a huge success. Adding sequences of sheer and deliberate quirkiness and humor, the attempts to fit in all it could didn't really affect the quality of the film for me. There was simply WAY TOO MUCH of the crafty creativity present to deny the excellence in filmmaking here.
Now, at first, when you think about it, Spiderman is taking on a lot. The Sandman is actually the man that killed Peter Parker's uncle and spawned his entire need to fight crime. A black, oil slick creature emerges from a meteorite and clings itself to Parker, amplifying his emotions, especially on the negative side. Talk about a change of face and hair. He ends up even striking Mary Jane Watson and nearly blowing up his friend Harry in a fight. Speaking of which, Harry gets amnesia in an initial fight, then attacks Peter in a personal dual in the best way any villain can. Through 'MJ'. Then, when things look up and Peter sheds this black ooze off of him, he ends up basically creating a fierce enemy out of a rival photographer he humiliated badly. etc. etc. etc.
Now for the shocker! The overload in events is exactly what Spiderman needed. The whole point of all this is that Peter Parker's emotions have always created a cloud of confusion around him. Now that they're amplified, he's made enemies out of some dangerous people, namely Brock, the Sandman, and Harry; and then out of people he really cares about, namely MJ. The end of the movie is a sum of all that he's created after becoming the black suited spiderman, and it's something that nearly kills him. This is pretty much a life lesson that we all create the world in which he actually live. That is a powerful and blatant message that can't be ignored.
Sure there isn't much explanation on the Black ooze that eventually becomes the "Unamed" VENOM, but what more is there to say? It's a black substance attracted to high states of emotion that is harmed by resonance and it will cling hard to a victim and amplify their emotions to the state of madness. Sounds like an explanation to me. And the Sandman. Does he need more? He's doing what he does to try and save his daughter's life. He turns into an invincible and powerful guy and doesn't follow the same path as Spiderman. Instead, he uses his power to do anything he can to save his daughter. That's the point.
I'm not saying that it's not a lot to take it, but let's break this down into simplicity. We're asking for more and we're asking for less at the same time. I'll admit that the action in Spiderman 3 wasn't as crafty at the second. It had amazing special effects and it was nail biting still. The story itself was better. It went from bad to worse, to worse, to even worse than that, and then ended so bittersweet, you have to know that Spiderman 4 is around the corner. It's the end of a trilogy, but it's just the beginning of something more, if all the right people come back and WANT to do it.
So... an A? I don't think that's over rated at all.