I don't think Sherlock Holmes is languishing in obscurity - in the last couple of years there's been a new movie adaptation and a (far superior) TV series. The original books are old enough now that they would be public domain, even in the US?
Sorry for not being clear. I was citing Sherlock Holmes and Frankenstein as examples of famous characters that are in the public domain. (Holmes's situation is in fact a bit murky in the US)
