Chris lee and his role as Saruman.

[The Only Real Estel]

What if Chris Lee was Cast as Gandalf? This could just be me but I can not imagine anyone being Gandalf except Ian Mckellan. Even such a great actor as Lee, I just don't see him fit for the Gandalf role.

Well, I know I can't imagine anyone else playing Gandalf than Sir Ian, but if Christopher Lee had played him, then it be the exact opposite, as it usually is with just about everyone .
Still, I think McKellan was the best actor for the role, Son of Numenor said it well when discribing Lee's ideal role:

Lee...who is the master of playing the Cold, Well-Spoken & Cunning Villain.

Lee was in his element when he was playing Saruman, the character played well to his strongest traits, much more so than Gandalf would have. I have no doubt that, given his talent, Lee could've still made a decent Gandalf, but McKellan was simply the best choice for the role. As Gorwingel brought up, Ian was much more suited for the wizard because of his age, but his voice was also so well-suited for it. Lee's voice just isn't quite Gandalf, if you know what I mean, I think he would still be off even with his best effort.