You are confusing two different terms. Cider is a translator, not a port. A port is when they actually rewrite code to fit a new platform, where as a translator just takes the language and APIs and translates it as best as possible.
OS X is lacking in the sets of APIs compared to Windows, which video card hardware takes advantage of via Direct X. However, Apple with the release of 10.5, did toss a bone to the developers called Core Animation.
Apple is still coming in late into the game. Give them some time and if the market catches on you will see more robust API support for hardware and gaming on the Macs.
