Have to disagree with you on this one Joe, Raimi absolutely had originally cast Malkovich as the Goblin - in an early draft of the script, both the Goblin AND Doctor Octopus were featured, but they (rightly) decided one villain was enough and excised Doc Ock, saving him for the terrific second film - I remember vividly the press reportage on it, Malkovich had to back out because he was shooting the other Mr. Ripley adaptation (the one without Matt Damon) at the same time.
But you are correct that Raimi wanted Malkovich for the Vulture (he also strongly considered Ben Kingsley for the role as well, and he very nearly signed up for it), but that was proposed for a fourth Spidey movie that never came about, mainly because Raimi allegedly hated all the drafts submitted at that time, and thought the pre-determined release date was too tight to really make the film as good as possible- that and the fact Sony wanted the budget considerably lower than the reputed $260m that the underrated Spidey 3 cost- personally I'm glad they didn't make a fourth one as there was nowhere left to go, pretty much everything had been wrapped up and doing another one just so you can see another of the villains from the comic-book onscreen is not a reason...