Re: Guest villians you would have loved to have seen back in the 70's
Raymond Burr, Elizabeth Montgomery, Gregory Peck, Hal Linden, and Tony Franciosa immediately come to mind. George Peppard could have given a smooth performance, and Burgess Meredith and Ben Gazzara were two almost-stars I'd have liked to have seen make the show.
Re: Guest villians you would have loved to have seen back in the 70's
Howard Duff.
He appeared in just about every series of the era (even as the killer in Ellery Queen), and I've always been puzzled how a spot in "Columbo" could have escaped such a great character actor.