Back to early 90's - XCOM aka UFO returns (via an open-source remake). Happily, nearly trivial to build on OSX.
Grab the source. Github has a nice OSX client, and the webpages have a wee button to spawn the OSX client and make the git clone process painless.
Get a packaging system for install Unix packages on OSX - the new hotness is Homebrew, in addition to fink or macports. Homebrew has the relevant dependencies, so it works (tm).
brew install yaml-cpp
brew install sdl
brew install sdl_gfx
brew install sdl_mixer
set the pkgconfig tools environment variable to find the installed stuff.
In the src directory of OpenXcom
And tis done. Copy the games data files to the relevant location, and all is well.