Riddle of the Sphinx has a Mac version.
Timelapse has a Mac version.
Myst, Myst Masterpiece, and RealMyst have Mac versions, though you need a fast computer for RealMyst.
Riven works with either PC or Mac.
Myst III: Exile works with either PC or Mac
Morpheus works with either PC or Mac.
Chemicus, Physicus, and Bioscopia all work with either PC or Mac.
I've heard there is a Mac version of Amber, but it's very hard to find.
Alida is made for Mac only. There are separate versions for OSX and for "OS9 and earlier." http://www.alidagame.com/