The perfect actors who I thought I would been good for Magneto, but their not that well known. 1. Michael Nouri 2. John McCook They have that white hair that really favors the one comics and both have this really baritone voice to go with it as well as kind stern presence.
I think Rutger Hauer from his Blade Runner days was an inspiration for how Magneto was drawn. The X-Men artists from the 80-90's were influenced by scifi/horror/fantasy movies. If you ever read the books then and had seen From Beyond, Blade Runner, and A Clockwork Orange you would've recognised where they borrowed their ideas from.