Seeing as how we're dealing with a) a movie series, where each is made to leave the door open for a follow-up and thus each is dependent on the next and b) a movie adaption of a comic series that's over 40 years old (and one that has been reinvented in comic form a few times itself) I'm going to try to tone down my comments on the story aspects and focus more so on casting and characters.
And so here we go.

Spider-Man

The Good: The first movie, directed by Sam Raimi (Evild Dead, Dark Man), basically an origin story. Tobey Maquire, turns out, plays a great Peter Parker. I don't think anyone could've captured the teen awkwardness, the social failing of the young Spidey. The costume is done well (despite the odd dimensionality of it), and the story really shows the character of Spider-Man well. And Kirsten Dunst plays a good Mary Jane as the girl next door, the high school crush. Aunt May and Uncle Ben work for what they are, so no complaints there.

The Bad: While Kirsten does Mary Jane as she does, she still isn't what I'd call "hot". No offense, but when I look at her face I don't lose myself or some shit.
The Osbournes. I'll sum up quick. Defoe: not physically dominant enough for the role of Norman. Franco: not physically inferior and timid as of the character of Harry. In the comics Harry is in some ways more awkward than Peter, but he's granted acceptablity because of wealth. Here, Harry is more the cool bad-ass who flunks his way through life.
Also to note: Spider-Man's internal webbing. I know now they've gone internal, but at the time (and for the nearly 40 years prior) he relayed on his web-shooters. At the time unforgiveable, now I could live with it.

The Ugly: That pug ugly Green Goblin costume. Look at the comic, look at the movie, need I say more?

How Close to Perfect: 8/10 This is really how comic book movies should be done, and this movie really pulls off the origin story awesomely. Considering how many years of material to pick through and how many variations of Spider-Man have been done both in media and comics, this really comes pretty close to perfect. The only faults fall on the supporting characters casting and that damn Green Goblin costume.

Spider-Man 2

The Good: It's hard not to start off with how great this movie is, how Raimi's horror background shows up as a positive, or how this is just one of the best superhero movies out there. That's my mention, so I'll try to move on. This movie feels more like a comic book, and while the first one was a standard bearer, this one isn't slowed down with half the movie as an origin story. Translation: more action from start to finish. And if you had any doubts left over about Tobey Maquire after the first one, they should be thoroughly crushed by the end of this flick. Oh yeah, and (surprise!) Doctor Octopus actually has moments of greatness as a villian.

The Bad: Can something be a good thing and a bad thing at once? That's the question Doctor Octopus raises in this movie. He doesn't look like the fat schlub from the comic, he doesn't have the green jumpsuit, and the arms are so much cooler than the comic book's depiction. And to me, Doc Oc always came off as one dimensional to me, really lacking character. Villian of the Month. But here he has depth, driven to crime because the AI in the arms convince him to. All this sounds great, but the problem here is it doesn't match the comic book. And folks, that's what we're really focusing on. So while he's a good villian in this movie, he isn't the true Doc Oc that we're expecting.
Now I wasn't reading comics my whole life, but did Peter Parker really ever have it THAT bad? He really at one point has the whole world kicking him in his sack, and the best he could do is say "more? Sure, why not!" But hey, maybe I just missed that part of Spidey's life.
Other faults go back to casting from the first flick, so I'd be repeating myself.

The Ugly: Not much in ugly. In fact by breaking away from the comic book likenesses we are spared the ugly. Can you imagine if they actually DID have Doctor Octopus look like his comic book namesake? Ugh, that would've been ugly.

How Close to Perfect: 7/10 While this movie feels more like a comic book, the fact is Doctor Octopus really strays far from the course. Too far to overlook. Don't get me wrong, I really feel that this movie is a better viewing experience than the first (more action, greater fight scenes), but is it accurate? No, it's not.

Spider-Man 3

The Good: The third movie brings us Spider-Man in direct conflict with Harry Osborn (the New Goblin), the Sandman, Eddie Brock (Venom), and himself via the Black Symbiote Costume. It also brings us Gwen Stacy and her father Chief Stacy (sorry comic fans, I forgot his first name).
Sandman, though often made monsterous in this flick, also looked AMAZING, and yes, pretty dead on (with the hair cut being the only exception) I don't know how or if they changed his origin, but he did come off cool on screen.
Gwen Stacy was also pretty much spot-on in appearance. Oh, and hot.
Spider-Man gone Black. I liked the edginess of it, even the My Chemical Romance look Peter rocked out when walking about town.

The Bad: Gwen Stacy: the character. See, though if it wasn't as obvious in the first two, it becomes blinding here. Mary Jane is a total Gwen Stacy (from the comic) character, while Gwen Stacy is lacking. Filler even. MJ here is Pete's high school crush and first love, completely innocent, the object of competition for, and get's tossed to her (near) death by the Green Goblin. These are all the things that Gwen Stacy was in the comic book. Meanwhile in the comic MJ was Peter's second love, a fall back off Gwen Stacy, and someone who is more a bad-girl, wild-child. Dudnst's peformance of her as a high school crush was alright, but as Peter's adult love interest doens't seem to match up.
And to me it is just a bit weird to have Gwen date Eddie when neither ever met in the comic.
The New Goblin costume. It just doesn't say to me "Goblin"; it says to me "EXXXTREME!" But at least it beats the first movie's Green Goblin Costume.
The Black Spider-Man Costume. It really just looked like a black & white version of the red & blue. And where's the big, white Spider-Man symbol? That symbol is crucial to it's coolness factor.
Repentemt Sandman. Be a villian for fuck's sake. Enough of these "I don't want to be a bad guy, really, I don't!"
One more thing, and as my friend put things, "Happy Harry". I've never seen anyone happier to have amnesia.

The Ugly: The difference between Peter Parker, before, after, and during his Black phase. It wasn't as noticable in the previous ones, but this one they REALLY push him as a total geek. Total, complete, dork. Even as Black he still shows some signs of it, but they contrast it enough.
Oh yeah, since when does Peter know how to play piano like a pro? Do alien lifeforms give that skill?
And speaking of alien lifeforms, how disappointing is Venom? First we cast Topher Grace (best known as skinny Eric Forman from That 70's Show) for the part, when last I checked Venom/Brock was totally jacked up in the comic. From serious/scary to wisecracker? What the fuck? And then we have the costume which, well, didn't see a big, white spidy symbol on that either. And finally he dies in his first fight scene?! NO!!!!!

How Close to Perfect: 4/10 Sandman and Gwen Stacy appear spot on. Venom, Harry's Goblin, and the Black Costume not so much.
Here's the thing. Sam Raimi is a Silver Age Spider-Man fan. It's obvious, and I'm sure he's admitted from time to time. He wanted to capture as many aspects of the Silver Age as he could and put them in a modern setting. But he ran into a problem: Peter's SA girlfriend was Gwen Stacy, while us Modern Age readers only really know Mary Jane Watson. So what's his solution? Combine the two. Give Mary Jane Gwen's personality and (some) history. That would be all fine and dandy if he kept Gwen out of this one. He didn't. I mean, what about Felicia Hardy (Black Cat)? You know, who actually had a thing for Spider-Man when he went Black. Oh wait, that's modern age.
Fact is everything involving the Black Costume is. It's origin (which involved every hero in the Secret Wars) to it's removal (thanks to the Fantastic Four), to where it ended up... on Venom (arguablely the most important Spider-Man villian of the Modern Age) Even Sandman often requires some extra hero help.
So you see, by even bringing up the Black Costume we were fucked because it's history is impossable to recreate without coming off as cheesy due to it's lack of the Marvel Universe at it's dispossal, and the fact that Raimi is NOT a Modern Age reader.
So the perfection rating suffers accordingly.