These are the Mac system requirements for running Starcraft 2:
Minimum Starcraft 2 System Requirements for Mac
These are the baseline specs that you’ll need to run the game, if you are near the lower end of the settings here you probably won’t have great performance.
Mac OS X 10.5.8, 10.6.2 or newer
Intel Processor
NVIDIA GeForce 8600M GT or ATI Radeon X1600 or better
12 GB available disk space
1 GB RAM (2 GB highly recommended)
DVD drive
Broadband Internet connection
1024X768 minimum screen display resolution
Recommended Starcraft 2 System Requirements for Mac
In addition to the system specs above like available disk space and an internet connection, to run Starcraft 2 the best on your Mac these are the recommended specifications:
Intel Core 2 Duo processor
4 GB system RAM
NVIDIA GeForce 9600M GT or ATI Radeon HD 4670 or better
Obviously the better and newer your Mac, the better Starcraft II will perform on it.
Starcraft 2 System Requirements for Mac