Late 2009 MacBook unibody (white) for gaming

Hey all, I'm going to upgrade the ram in my late 09 unibody macbook (white) and was wondering how much would be required to play (somewhat) ram and memory hungry games. Currently it has 2gb ram at 2.26ghz and a 250gb hd, it doesn't run games well at all, with even minecraft lagging considerably. All other use is somewhat laggy also.

So how would games like call of duty go on this computer? and what upgrades would be needed to make it run well, or will just a ram upgrade make it okay?

Don't tell me to buy a new laptop, I'm in no position to do so as the laptop is fine, just needs some upgrades.

Thank you!