Well, I'd love any good mystery movie. A while back I posted a question about other movies like Charlie Chan. If you go back a few months, you can probably find the message and the responses. I got a lot of great responses and a list of movies that I hope someday when I get the time, to watch!
Besides, of course Charlie Chan, I do love the Sherlock Holmes movies that have already been mentioned. Also the old b&w Dick Tracy movies as well. And Then There Were None was also a good movie. I still need to check out many movies/series if I ever get the time. We recently got a free trial to Netflix so hopefully that will give me access to some classics like Miss Marple and, as Rush mentioned, Poirot. I like the Mr. Wong movies, and hope someday to get the Mr. Moto boxsets.
I do like the old b&w monster movies: Dracula and Frankenstein and such and actually looking forward to watching them for Halloween! TV Show-wise that are non-mysteries, I like a lot of the classic tv shows from the 60s and 70s that I grew up watching on Nick-at-Nite due to my insomnia back when I was a kid heh. Shows like Get Smart and such.
Overall, I have a great appreciation for classic movies and tv shows and in most cases prefer them over movies/shows produced these days. But of course, there's always exceptions.