it depends on texture/polygon resolution, interference and even game engine. In general, the higher your screen resolution ("rendered resolution") is the less impact aliasing will have for you as it will be less noticeable, but if you are to zoom in at any of the aliased edges you'd still notice it.
The short answer is no, you do not need it to play video games. The bonus you get for enabling it is that aliased edges look smoother, so the graphics look more "natural" (ie you don't see jaggies in real life)