Which gen? The current gen of macbooks has these specs for GPU:
White Macbook: NVIDIA GeForce 9400M graphics
Silver Unibody Macbook: NVIDIA GeForce 9400M graphics
Silver Unibody Macbook Pro: NVIDIA GeForce 9400M + 9600M GT with 512MB (Non-SLI)
I'm sure you could run some source based games on the Macbooks, but anything more might need a more powerful graphics card. Macbook Pro's could maybe do a little bit more, but neither of them are built for gaming. Mac's are not gaming computers, they are student/photo/video computers. I suggest getting a PC though.. better deal, better components.
Macbook Pro 17":
2.66GHz Intel Core 2 Duo
4GB 1066MHz DDR3 SDRAM - 2x2GB
320GB Serial ATA Drive @ 5400 rpm
MacBook Pro 17-inch Hi-Resolution Glossy Widescreen Display
SuperDrive 8x (DVD?R DL/DVD?RW/CD-RW)
NVIDIA GeForce 9400M + 9600M GT with 512MB
For $2,799
Now, a nice Battalion 101 M571TU II (From IBuyPower)
Battalion 101 M571TU-U 17" WUXGA 1920X1200 Widescreen LCD TFT Notebook screen
Intel? Montevina Core 2 Duo Mobile P9600 Dual-Core Processor (2x 2.66GHz/6MB Cache/1066FSB)
4GB [2GB x 2] 1066MHz DDR3 SDRAM [Notebook Memory] Corsair
DDR3 1GB Nvidia GTX280
500 GB 5400rpm Serial-ATA-150 Super Slim Notebook Hard Drive
8x Dual Format DVD?R/?RW + 16x CD-R/RW Combo Drive [M570TU]
All for $2,179
Alright, lets see...
Same processor
Same Memory (Assuming Apple uses Corsair)
Macbook Pro has has a smaller hard drive
Macbook pro has a terrible GPU compared to that of the Battalion
Ok, so you get a smaller hard drive, and a worse GPU, and you pay $620 for it.
Now, lets see what you could add on to the Battalion to make it better, and the same price as the Macbook Pro...
Ok, look at this: Add a....
Intel? Core 2 Extreme Mobile X9100 Dual-Core Processor (2x 3.06GHz/6MB Cache/1066FSB)
and a
128 GB 2.5 inch SATA Gaming MLC Solid State Disk (Nearly Instant Data Access Technology)
AND THE Macbook Pro IS STILL $10 MORE!