Chris lee and his role as Saruman.

[Son of Númenor]

I think your answer to the second question answers the first as well. Obviously, Christopher Lee wanted to be in the movies, and who would turn down such a talented actor with such devotion to the material? It became apparent to Peter Jackson at some point during casting, if indeed it wasn't apparent from the start, that Lee's credentials, appearance and acting style made him far better suited to play Saruman than Gandalf. McKellen has a warmer demeanour and a seemingly humbler disposition than Lee, who is the master of playing the Cold, Well-Spoken & Cunning Villain. (Well, actually, he shares the honour with Jeremy Irons.) Although it is interesting to note that another actor originally chosen to play Gandalf was done away with a few days into shooting, McKellen was the obvious best choice (in the opinion of the majority, if I may speak on their behalf).

[Gorwingel]

Actually the true reason that Christopher played Saruman and not Gandalf (and I have heard him talk about this many times) was because they both agreed that he was too old, and that they needed a younger actor to play a character who is so incredibly active. Christopher Lee is actually 82 years old, and Ian is in his sixties. Mr. Lee would have most definitely have played Gandalf if the film would have been made years earlier. Though I don't think that Tolkien would have had a problem with the amazing performance that Sir Ian gave (In my opinion he didn't just play Gandalf, he became Gandalf )

[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.

[Boromir88]

Yes, Chris Lee does have that Saruman type voice, really not fit for Gandalf. Son of Numenor pointed out Chris Lee's talents as a villain, many of the movies Lee was in he was the villain. I mean Dracula, The Gremlins (2nd movie), and Star Wars Episode 2, are the movies that come to mind where Lee has played sort of that bad guy character. I can't really describe Lee's voice, it is slow and powerful, just really the perfect voice for Saruman, as Saruman was known for his ability to persuade. 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. Lee really brought out Saruman's character, as well as Sir Ian did with Gandalf's.

[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.

[Lobelia]

Originally Posted by Boromir88

Yes, Chris Lee does have that Saruman type voice, really not fit for Gandalf. Son of Numenor pointed out Chris Lee's talents as a villain, many of the movies Lee was in he was the villain. I mean Dracula, The Gremlins (2nd movie), and Star Wars Episode 2, are the movies that come to mind where Lee has played sort of that bad guy character. I can't really describe Lee's voice, it is slow and powerful, just really the perfect voice for Saruman, as Saruman was known for his ability to persuade. 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. Lee really brought out Saruman's character, as well as Sir Ian did with Gandalf's.

Christopher Lee may be a great villain, but he is quite capable of doing warm, endearing roles as well. I've seen him play a wonderful, twinkle-eyed wizard in an otherwise awful TV series about Robin Hood and, in the Tolkien Ensemble's CD At Dawn In Rivendell, he is a superb Treebeard, far better, dare I say, than John Rhys-Davies, delightful as he was in the films.

[Essex]

And vice-versa, Sir Ian can definately play a baddy role. eg Magneto in XMen(s) and, of course, Richard III, the biggest 'baddy' in ALL literature.

Gorwingel is right as to why Christopher Lee did not play Gandalf. If you watch the Cast Interviews on the DVD Extended Edition of The Fellowship of the Ring it is explained there.
The role of Gandalf was physically demanding. Riding horses, walking, running etc. It also had a greater time commitment. Christopher was realistic enough to realize it would have been too much for him.
I believe he would have made a fine Gandalf had he been younger. He looks (and sounds) great for his age!

[Lobelia]

Originally Posted by Essex

And vice-versa, Sir Ian can definately play a baddy role. eg Magneto in XMen(s) and, of course, Richard III, the biggest 'baddy' in ALL literature.

Ooh, yes, absolutely! I saw the Richard III film first and thought him wonderfully villainous, though I had some sympathy for Magneto. Just goes to show both of them are wonderful actors who can act rings around many younger stars.