playing bf3 on ultra above 1400 resolution will use more than 2GB VRAM so if in the future you were going to get a monitor that can do resolution that high then you will need more than 2GB VRAM. Also i believe skyrim with the extra textures and graphics uses over 2gb
for bf3, nvidia cards will still get better fps than ati cards at any resolution
http://www.anandtech.com/bench/GPU12/477























