The bad news is, what you've heard is technically true: "Spider-Man 3" is, when all is said and done, just a bit overstuffed.
The good news - the very, very good news - is that it's not overstuffed for the reason most were worried about, i.e. "too many villains." If anything, this is the least "bad guy centered" "Spidey" entry yet. Whereas the prior films featured singular antagonists (Willem Dafoe's Green Goblin, Alfred Molina's Doctor Octopus) with character-arcs detailed enough to take up a full half of their respective films, the three heavies this time around are a bit more on the dramatically-streamlined side: Two of them have pretty basic ambitions and straightforward, uncomplicated agendas, while the third (James Franco's Harry "Goblin Jr." Osborn) already did his "turning into a bad guy" arc in the backdrop of the prior installments - he arrives here as a full-fledged nemesis ready to go from (literally) the first act on.
Instead, "Spider-Man 3" is bursting at the seams with story. Director/co-writer Sam Raimi has a lot of plot threads left to tie up from his previous two movies to begin with, and on top of that he's piled surprising reversals, character-twists and unexpected new directions and revelations - and then some. There's enough going on here in the living, breathing universe this cast and crew have built for themselves over the last eight years to fill three more movies - and, save for some irritatingly-noticable contrivances here and there, it seems almost churlish to take a summer blockbuster that could easily have coasted on residual narrative-fumes and perfunctory action scenes to task for wanting to have "too much" story, character-development and narrative gotchas.
In the big-picture sense, Raimi demonstrates once-again his unquestioned "getting" of the key Spider-Man themes; framing this third go-round as a rude-awakening "oh yeah?" rebuke of "Spider-Man 2's" fairytale ending. Turns out, wouldn't you know it, grand romantic gestures like Mary-Jane (Kirsten Dunst) dashing out of her wedding and turning up on Peter Parker's (Tobey Maguire) doorstep aren't quite 'grand' enough to stave of harsher realities forever. In the time between that ending and this beginning, things have started to go wrong. And, for a change, not "supervillain-assisted" wrong... just "that's life" wrong. In fact, it would seem the two of them have managed to "swap" issues: As New York begins to overwhelmingly embrace Spider-Man as it's resident champion, Peter is letting fame and acceptance go to his head a bit - he's almost too distracted to notice the MJ's Broadway "star" has already started to wane, and that she's picking up the 'sad sack' right where he left it off. Also on the list of things Peter should be paying closer attention to: Harry still knows Spider-Man's secret identity, he's still convinced that Spidey murdered his father, and he's still got an attic full of dad's old anti-Spidey weaponry to play with.
The choice of new villainy also demonstrates a tremendously-appealing confidence on Raimi's part - both in his own skill and in the strength of the original material he's adapting. Other lesser genre entries like "Fantastic Four," "Daredevil" or (from the looks of things) the upcoming "Transformers" movie tend to flee in mortal terror from the more "out-there" concepts of their ancestors. Raimi and his film, on the other hand, fearlessly drop into an already well-stocked narrative a pair of supporting supervillains who each constitute the franchise's headlong-leap into the realm of full-blown pulp science fiction: Sandman, aka Flint Marko, (Thomas Hayden Church,) is a small-time escaped convict who, after an accident of science, has a body made of sentient, shape-shifting SAND; while Venom is, literally, a Monster From Outer Space.
Technically speaking, Sandman isn't so much a "supervillain" as he is a hard-luck crook with his own agenda who's aquisition of super-powers is more distraction and hindrance than benefit: He turns up on Spidey's radar mainly because of a "maybe": Marko, it turns out, was the accomplice of the robber who murdered Uncle Ben Parker - and may have been the one who pulled the trigger. On top of all this, Peter has an unethical rival at work in the personage of Eddie Brock (Topher Grace,) his ongoing Harry troubles, MJ's emotional distance AND jealousy over his in-costume flirtation with freshly-rescued blonde bombshell Gwen Stacy (an almost-criminally gorgeous Bryce Dallas Howard); a whirl of stress and dissonance that makes him perfect prey for Venom - a liquid-goo alien "symbiote" that slithers out of a crashed meteor and morphs itself into a sleek new black Spidey-suit that cranks up Peter's powers... but also leads him to indulge his dark side.
It's with this "symbiote" subplot that Raimi and company tip their most devious hand - turning Spider-Man/Peter Parker into the prinicipal villain of his own movie. Most of the time, the "good guy goes bad" routine underwhelms in films like this, because the "evil" version of the hero turns out to be exponentially more-compelling and watchable than the "good" one (looking at YOU, Anakin Skywalker.) But, through guts and willpower, the same fate doesn't befall "Spider-Man 3." 'Bad Peter' is 'dark,' yes... and you can tell Maguire had fun (literally) letting his hair down and playing against-type. But Raimi's camera and story-structure make the difference, lingering on the bewildered/disgusted reactions of women Peter shoots winks and leers at as he struts down the street utterly convinced of his own coolness, and building an almost unspeakably crass display in a "dance sequence" to a genuinely shocking "line-crossing" level. 'Bad Peter' is a sleazy, unlikable jerk; and even though most of the audience won't be TOO worried about him not snapping back to normal by the end credits, it's still brave of the film none the less to ask them to follow him down this particular road.
Unfortunately, all this good comes with a few notable "issues" that keep it just shy of the near-perfection that was "Spider-Man 2." Most of the missteps are structure and pace-related, i.e. the two and a half hour run-time isn't quite expansive enough to contain all the movie it needs to. As a result, some elements arise in questionable, artificial-seeming ways. This becomes especially apparent, though not disasterously-so, in the third act where the innevitable Bad Guy Team-Up seems to come almost-completely out of left-field, and the "things we really should've told someone BEFORE right now" revelations start to stack up. This is more than a bit forgivable, though, when one takes into account that it leads into an action sequence that could easily be the best "guys with super-powers" brawl since "Superman 2."
Other problems have "followed" from the previous movies: Kirsten Dunst is STILL the weak link of the series, it's three movies in and she still alternates between looking bored, stoned or eager to get on to something "better." And Raimi still hasn't lost his strange penchant for having Spidey lose all or most of his mask midway through nearly every action scene.
It does seem as though the writing is on the wall as to this being the "last" Spidey installment for this full group of castmates and filmmakers. If so, they leave behind quite a legacy: A true epic-in-three-parts superhero story, one of the only one's not to stumble in the third entry. Whatever comes next has some big boots to fill.
FINAL RATING: 8/10