You said Counterstrike. Is this Counterstrike 1.6 or is it Counterstrike Source?
Counterstrike 1.6 should run without any problems on your Macbook. What OS are you you using? My dad has an IBM with a x3100 (same integrated graphics in the current Macbook) and has problems with the old Half-Life engine games (like CS 1.6).
Counterstrike Source. Well, you have integrated graphics.
And while -dxlevel 81 will help. You can even put in -dxlevel 70, which should help even more. But to put it simply, integrated graphics can't run games. It doesn't matter how much RAM you install on your laptop. You can't compensate for the x3100.
Turning down all the settings and running in DX7 (the command I gave you, which goes in the Launch options) will help. There should also be some custom config files you can find online that are optimized for performance. I don't use them, so I can't tell you where to look or where to find them, asides from doing a google search. But don't expect any miracles.