I have long been an unabashed fan of the Spiderman movies. In my view they stand head and shoulders above all their spandex-and-CGI counterparts. While Batman Begins garnered much praise for being "dark" and the X-Men movies had decent acting, these movies were too busy delivering fast thrills to pay attention to characters and themes. In contrast, Spiderman is from beginning to end all about the travails of being human, and executed with such delicacy and humor that the action, while engaging at times, exists to heighten the drama rather than to provide it in the first place.
The third installment is definitely the weakest, as many critics have said. There are too many villains, and at least two of them--the black ooze from space and Topher Grace with a bad haircut--fall into the story so arbitarily that it's almost silly. The writing doesn't always have the nuance of the previous movie, where the hand of Michael Chabon was beautifully in evidence. And the first half of the movie juggles so many disconnected elements that it's hard to see how the ending can possibly justify the buildup.
However. What this movie never does is wander off into a CGI-packed wonderland that forsakes character development for explosions, as so many other movies of its kind would do. Raimi demonstrates once again that what interests him the most is the human element, with every character--even the most minor--asserting some level of importance simply by virtue of being human. This is made most apparent with the villains, all of whom are driven by motives that are on some level justifiable--there is no one to purely hate. Harry is, at worst, deeply misguided; and the Sandman is a classic case of a man who blundered too deep into crime to find his way out. Eddie Brock, a deeply unlikeable photographer who competes with Peter and later becomes yet another villain, is driven to cartoon evil by genuine despair and failure. Peter's conflicts with these villains evoke a measure of internal conflict in the viewer.
But this is the heavy stuff, and it would be a pity if I neglected to mention the delightful J.K. Simmons returning for another hilariously cantankerous stint as editor of The Daily Bugle; then there's his secretary who has a soft spot for Peter, Peter's Russian landlord who gives him vintage Old World advice about women, and the landlord's daughter who provides many moments of sweetness and humor. That's leaving out the main actors, because there's really no need to mention them; but perhaps it should be noted that Harry's vulnerability is particularly affecting.
The major theme of Spiderman 3, when it emerges, is that there is a fine line between a hero and a villain, and Peter spends most of the movie teetering on the brink. A common comic book theme and executed reasonably well when the plot isn't dithering too much; but for me the best moments were the tiny human details: the sly French maitre d' who conspires with Peter in his proposal to MJ, the way Peter echoes the thoughts of many viewers after one of his encounters with the Sandman, as he shakes the sand out of his clothes and mutters "Where do all these guys keep coming from?" In acting there is the concept of "the moment before," when the character is inspired to action; Raimi often focuses on the moment after, the less dramatic but intensely real aftermath.
And like the previous two movies, Spiderman 3 is a love song to New York, depicting the city as a mythic realm both of opportunity and deadly loneliness--a place where superheroes are needed most.