Crysis 3
Crysis 3 is a beautiful-looking game that continues to tax high-end systems. We've benchmarked a 60-second section near the start of the game, with lashing rain, numerous reflections and full DX11 pomp on show. 4xMSAA is enabled at 1080p and disabled at 4K.
4GB framebuffer? 8GB framebuffer? It makes no difference in Crysis 3 - the engine laughs in the face of modern GPUs.