I've not seen the Ross Martin movie and have only seen brief moments of the Naish TV show, but I have watched the other two.
One can enjoy the Ustinov movie if you don't treat it as a Chan movie but view it as '70s kitsch/fluff. It has some good actors in it that make it a tolerable viewing experience. Had the script been written straight Ustinov might have been a good Chan, but I can not in good conscience call him Chan in the sense that Oland was. The DVD cost me something like $6 and it had some interesting featurettes about the low budget studio that made the movie so I feel I got my money's worth.
Murder By Death is one of my favorite movies and despite some qualms with the language in it, I can watch it repeatedly. The only downside to the Sellers portrayal is that some unenlightened folks have taken his farcical over the top portrayal & make-up and assumed that this applied to the Chan series proper. I can't tell you how frustrating it was to see papers like USA Today and others say that the Chan movies featured an actor in yellow make-up and buck teeth.
Steve
PS - got your e-mail...thanks, if you ever change your mind, the offer is still open.