A great article that should lay this contentious issue to rest. I have to admit this was an eye-opener for me. I thought more games would use the space afforded by modern video cards.
http://www.tomshardware.com/reviews/graphics-ram-4870,2428.html
Keep in mind however that this test is valid at this point in time. More buffer effects, bigger textures, etc. Like Doom III was back in the old days, GTA IV is an excellent example of a game which requires will use all the VRAM you throw at it. The difference between 256 and 512 is stark.
