I really think Maguire did play early Parker quite well in the first movie. He goes from a nerdy geek to losing his glasses and was considered good looking when the first movie opened. He did pursue MJ before he didn't know he could have her. He did hit on her and started talking more. He did stand up to Flash, started talking back to Uncle Ben and I think he got pretty damn angry when Uncle Ben died and when GG thratetened to kill MJ...among other things at the end. Or when she was kidanpped by GG to begin with.
Sure in sM2 he regressed back to nerdy introverted Parker for over a third of the movie, but that was the point. He was trying to regress to a time in his life when things were simpler and be himself. He started wearing glasses again and the whole nine yards but then again he also became more vocal with MJ and going after her. He also was one to show anger or annoyance in the heat of things. He didn't take crap from Ock or the train instructor, etc. Sure he took it from Connors and Harry but one was his best friend and the other was his professor. He isn't going to talk back. Same with Jonah (though he is less pushed around in SM2 and he takes charge with symbiote in SM3). And his taking his mask off in front of Doc Ock made sense for the character in that he knew he couldn't stop it himself and he had minutes or less to save their lives along with the rest of Manhattan's. He thought it was the only way to get through to Octavious so he made a quick decision. It paid off. And that shot of him looking back at Ock captures the quiet nobility that Parker in the comics has always had and turning around to see MJ. To me the movie reached a level of unsurpassed quality in a superhero movie from that moment to the final shot. It was just perfect.
If anything I felt he became a little geekier at the beginning of SM3 to make the transition to Dark Parker more surprising and startling. Though he acted more confidant as Spider-Man and more of an adult as Peter. And by the end he didn't say a word to get MJ back, but quietly took an adult step at forgiving each other and not saying anything. He finally grew up at the end of this movie.
I think Maguire captures early Parker and his quiet nobility (without having an inner-monologue to help, except in the notrious grave scene at the end of SM1) that has always been prevelant. No he doesn't make a lot of wisecracks. I think it is partly because they would hamper action scenes if he was joking all the time but he has a few at the same time I think it is a distrust in maguire's delivery (though I thought his wisecrack delivery in the games SM1 and especially SM2 were good. In the SM3 game though he just sounded bored).
In the end I think Maguire is a very strong nuanced character actor. He doesn't play broad in the classical sense. In the Spider-Man movies he plays his character broad but he prefers inhabiting the character than performing the character for the audience. He seems to want to just present his interpretation of the character. It is why he was so good in Cider House Rules, Seabiscuit, Wonder Boys, Pleasentville and a favorite of Ang Lee in Ride with the Devil and The Ice Storm.
I don't think Jake Gyllenhaal is nearly as good an actor. I think he is more a movie star persona. Though he proved to be decent in both the films October Sky and Donnie Darko and has sense actually proven to be a very good actor in films such as Jarhead and Brokeback Mountain. But he still uses the performing persona. He is less of a character actor than a star actor in that compare his very heavy handed approach in Brokeback Mountain to Heath Ledger in that movie or Maguire in Ang Lee movies.
I think fans want that type of acting from Spider-Man but I think we have such a good actor doing it now, I'm not in a hurry to lose him. Especially since the story he started to tell isn't over (Pete and MJ aren't married yet). But fans want their Hugh Jackman in the role metaphorically speaking which is why Jake G is so popular as a replacement. That and he is more handsome, but that isn't a big deal to me.
However, I will point that Sony will likely replace this cast with actors who are going to probably be playing the Maguire interpretation as to ensure formula success for Sony, so don't expect Parker to be the college swinger he became, at least by graduate school in the comics where he had every woman he met throw themselves at him. Oh well.