Unity3D has publihed the result of their hardware survey. Unity3D targets the casual gamer and here are some pictures about what is graphics card of the casual gamer:

Casual gamers are really not interested to performance since around 3% of them haven’t graphics drivers… Most of the graphics cards are integrated chipsets (Intel, S3) and the first decent graphics card is the GeForce 8600 with is ranked 15.
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via drawlogic