Age of Empires II, 4x4 Evolution II, Tropico, Warcraft 3 (Frozen Throne, Reign of Chaos), Caesar III, Civilization III, and America's Army 2 run just fine on mine. Not the greatest games, but then again it's not a gaming computer...if I wanted games I'd buy a PS2.
Running OS X with anything under 256mb of ram is akin to trying to tow a 10K pound boat with a Geo Metro...it'll move it (budge might be a better word than move), but you won't get anywhere fast and you're bound to screw something up sooner than later. I personally wouldn't use anything less than 512mb (laptop or desktop, g3 thru g5) for general use. The more you have the better.