Actually Kirsten Dunst did look like MJ in first Spider-man movie, but script failed to capture real MJ personality. She was just... well Kirsten Dunst.
In part 2 and 3 she changed her hair, and she look nerdish and with her teethes she reminds me of poodle.
And Gwen... well I don't need to say anything, it was horrible.
And I don't even want to speak about Tobey Maguire as Spider-man or Topher Grace as Venom. Topher Grace was ok but that was NOT Venom. That was... well Bane of the Batman Forever movie wearing black tights
But I think that Thomas Haden Church was kick ass as Sandman. No only that he look like Sandman in comics, but he perfectly catch his persona.