With the development of cloud-gaming, MAC users will be able to play more titles in the future. Turning a PC based MMO game into a MAC based game is not an easy task and it requires additional developers and it increases the cost for the development studio.
While, most publishers aim for more accessiblility, this is usually the choice of the developer. Unfortunately there are client-based MMO's that are only compatible with Windows OS based computers, aka PCs. So which MMO games work on Mac? Generally speaking, Browser based MMO Games are compatible with Mac. Games on PC don't work on Mac OS unless the developer has made the game multi-platform.
Each of the operating systems have different architectures and they have different software. First of all, what is the difference between Mac OS and Windows OS? Mac OS is a Unix based operating system with a different GUI than Windows.