A lot of MY absolute favourites are
veeerrryyy old

and fall into the "Classics" category but many of them
can now be played again on modern machines thanks to those wonderful people who come up with magic installers
and companies like GOG and DotEmu who offer them ready tweaked and DRM Free.

As regards slightly more recent releases however (those that I have managed to get to from my ever growing "yet to play" stack) a few I have been greatly entertained by are :
Art of Murder Series
Carol Reed Series
Chronicles of Mystery Series
Ghost Pirates of Vooju Island
Last Half Darkness Series
Lost Crown Ghost Hunting Adventure
Lost Horizon
Sherlock Holmes Series [Frogwares]
All of which have probably been mentioned here already !!
But further endorsement can surely only be good
