RF on Mac
Use the Bootcamp application on your Intel Mac (it must be Intel) with OS 10.4 or later. You will also need to load a working version of either Windows XP, Vista, or Windows 7 as well as Real Flight. Make sure that your Mac meets the RF requirements for processor speed, memory, and disk space. Macs are generally made with higher quality and higher speed internal components than is the typical PC so RF runs almost flawlessly on a properly set up Mac. I have every graphics option turned on and set at or near the highest level on my very old Mac Pro and I typically get between 80 and 100 frames per second. No need for Parallels or any other virtual machine since Bootcamp is already part of the Mac OS. Just make sure that you use a Windows version that can run RF properly.
The only simulators that I know of that are written for Macs are the Aerofly simulators. Aerofly Pro Deluxe (available from Tower Hobbies) and Aerofly 5 run very well on Macs which have adequate resources but they don't have all of the features that RF has and they're put out by a German company. Most of the posts on their forums are in German.