The Apple computers today are great computers and can make an excellent gaming computer. However, if one of the primary reasons you're getting a computer is because of gaming we'd still recommend a PC over an Apple computer. Below is a short list of the main reasons why.
Game availability
Depends on which Mac, I have Pinball HD on my Mac Mini 2.4 Core 2 Duo and I just love the gameplay, However, The same game has a noticeable lag on my Mac Mini 1.83 Duo. (Running OSX 10.6.6 on both Mac's) +. You may not immediately think 'gaming' when you think 'Mac,' but there are tons of games for the Mac these days, and some of the most popular PC games are also available for OS X.
Although more game companies are releasing their games as hybrid games, meaning they'll work for both the PC and Mac, the vast majority of games are published for PCs running Windows. In some cases, you could be waiting months or years before it becomes available for the Mac. For example, Half-Life 2, a popular FPS game, was released for the PC on November 16, 2004, but was not officially ported to the Mac until May 26, 2010.
Apple computers with Boot Camp can run Microsoft Windows and in most cases run Microsoft Windows games. However, there is never a guarantee that this will work and you may encounter problems or performance issues and its developer will most likely not support it.
Hardware and upgrades
Apple computers do have a few upgrade options. However, when compared to the PC those options are next to none and often much more expensive when compared to the PC. For example, if you want a better video card, a PC has hundreds of options and a Mac may only have a dozen or less.
Any Good Games For Macbook Pro
Performance
The Apple computers do have great performance and often meet or pass the performance of a comparable PC. However, with the hardware options available for the PC and the many different ways to overclock a PC the Apple is no match. In competitive gaming, if you want to get the most frames per second, PC is the way to go.
Any Good Games For Mac Computers
Free games
There is an almost endless selection of free available games for the PC and greatly outnumbers the available free games for the Apple computer.