Chris lee and his role as Saruman.

[The Only Real Estel]

Gandalf, had more leadership qualities to him, it stated in ROTK, during the "Siege of Gondor" whenever Gandalf was around the hearts of men rose. Where Saruman, was more of a persuader, he had power and emphasis in his words to "poison" people's minds.

Another point on Lee's voice:

I think Ian had much more of a voice for Gandalf in the sense that he sounded inspiring, whereas Mr. Lee's voice is much more monotone. Of course he could change it somewhat if he was cast for Gandalf, but I'm guessing it'd still sound a little to monotone to really sound inspirational.