I completely agree. First of all MJ is a very insecure woman('cause of her dad) and every decision she takes is from that mindset. Realize how she always dates men of power or some sort of high status: Flash was the popular guy of HS, Harry was rich, James was rich and somewhat famous, etc. She did it because she was seeking validation from her father and herself.
The reason she fell in love with Peter in the first place is because he is the only one who made her feel worthy beyond her looks which was something completely new for her. Those type of things actually happen in real life.
In Spider-Man 3 she became even more insecure when she was fired(she felt exactly like her father used to make her feel) and Peter was becoming 'successful', she thought Peter might not think her "worthy" anymore which showcased her low self-esteem. You can notice all of this by paying attention to all her scenes, its actually there! lol
I haven't read the comics but from what I've read about her character the only thing that was missing in her character was the "party girl act", MJ is supposed to present herself as a fun, cocky and seductive woman to hide her insecurity and this never came across in the movies unfortunately because that would have made her an extremely compelling character but for the most part the writing of her character and Dunst' performance were really good. In fact she's probably one of the most compelling female characters in superhero movies along with Pepper Potts in Iron Man.
This post.

It's really late where I am right now, so I'll try to make this as brief as I can, but here are some of my two cents about Dunst's Mary Jane Watson:
First off, I am very much "over" the whole mantra about Dunst not being "hot enough." Move on, guys. Maybe it's because I'm a female myself; all I know is that I'm sick of hearing/reading it.
In terms of Dunst's acting in the films, I think she did a fine job. Don't get me wrong, I think that there are other actresses who would do a fine job as well, so Dunst isn't my "end all, be all" MJ. To be totally honest, though, she was my favorite character in Spider-Man 3, and the character that I easily felt the most sympathy for (I know this is an unpopular opinion). I've never interpreted her motives as jealousy for Peter's success in Spider-Man 3. I saw it as "hey, I'm being a supportive girlfriend for you, but I need some support too." Clearly MJ had self-esteem issues stemming from Spider-Man 1. Seeing the man she loves gaining success while she is going through a failure/stepback in her career (and being ignored by her significant other) is sure to cause some very strong feelings of hurt and loneliness. I don't know about anyone else, but when I confide in someone I trust wholeheartedly when something bad happens, the LAST thing I want to hear from them is "Oh, just cheer up! It'll get better! I went through this, so you can too!"
As for Kirsten Dunst's chemistry with Tobey Maguire, I totally felt it, from the beginning of Spider-Man 1 when Peter asked MJ to take a picture of her. Their relationship in the first movie was a case where it was set to make the audience root for the underdog to get the girl, and I think it was very effective. My favorite piece of dialogue between these two characters will always be when they talk about their aspirations and their future after high school. It's funny, charming, and heartfelt.
In Spider-Man 2, we were all supposed to feel a distance between the two, where both of them were longing for each other, but both were convinced that it wouldn't be able to happen. From MJ's perspective, the man she truly loves (and someone who genuinely accepts her for who she is) rejected her. That's crushing to any real human being. MJ practically was trying to force herself to move on because (a) she was seeking validation again to try to fill a void, and (b) her brain was telling her that she needs to stop waiting for Peter and get on with her life. These are normal human thoughts and emotions, in my opinion. Does it represent a perfect person? Of course not; it represents a complex human being. In Spider-Man 2, I believed that BOTH Peter and Mary Jane were very much in pain and very much lost. That's why, in my opinion, it's so rewarding to hear Mary Jane's speech to Peter at the end of Spider-Man 2. Peter Parker and Mary Jane Watson have always brought out the best in each other, and MJ's speech at the end of the movie displays that.
I would actually argue that the party girl act was shown for a little bit in Spider-Man 1. The way she acted around Flash Thompson and her friends ... Seemed very artificial and was a total facade. That's why I actually believe MJ when she professes her love for Peter at the end of Spider-Man 1 and Spider-Man 2 because he makes her feel like being herself is okay; that her flaws are okay to have and that despite her flaws, she is worthy of being loved by someone. Is that not a big part of what love is, anyway?
I've overall
always preferred Peter x MJ over Peter x Gwen (I'm not expressing hate towards Gwen, though!), because the romance has always felt more real to me. Peter and Mary Jane show each other their flaws, and in the end, they're still together. Like I said, that feels real (as real as you can get with comic books, I suppose). I think that Raimi's movies were overall successful in displaying that.
As for the "damsel in distress" thing, whatever. If I were dating a superhero, and his identity was discovered by a supervillain, I'm preeeettttyyy certain that I wouldn't be able to do much to defend myself. From a story-telling standpoint, the damsel thing worked in Spider-Man 1 and 2. The only time I felt it was unnecessary was in Spider-Man 3 (because we had already seen it before twice, AND it would have made more sense for Gwen or even JJJ to an extent to be kidnapped by Venom). That's on the writing though, not Dunst.
As for "comic book accuracy," I think the only thing worth noting that wasn't exactly like the comics with Dunst's MJ was the amount of spunk and sass. She had some of it, but definitely not to the extent of the comic books. Dunst actually reminds me a lot more of the 1990's cartoon version of Mary Jane, who pretty much kept her sass and sexuality at a "PG"-level.