3. Vincent Price
The 1976 serial The Brain of Morbius owes a lot to Frankenstein. As a result, the storys director Christopher Barry was inspired to cast a horror film icon in the role of the nefarious Dr. Solon. Vincent Price was seriously considered, as was Peter Cushing who had played the Doctor in two non-canonical films in the 1960s. In the end, the role went to reliable character actor and Who alumnus Philip Madoc. Its not clear if Price was ever formally approached or even in the UK at the time but he would undoubtedly have made a formidable foe for Tom Bakers Doctor. As a footnote, Baker wrote the script for a Doctor Who movie that was never made called Doctor Who meets Scratchman. He had Vincent Price in mind for the titular villain.