Crysis 2 uses a development of the Crysis Warhead engine optimised for efficiency but adds DirectX 11 support via a patch and this can be quite demanding. As, for example, with tessellation, implemented abusively in collaboration with NVIDIA with the aim of causing Radeon performance to plummet. We have already exposed this issue here
We measured performance with Fraps on version 1.9 of the game.
The GeForce GTX 680 is hot on the heels of the Radeon HD 7970 here, while the GeForce GTX 670 is a little further ahead of the Radeon HD 7950. A good model of the GTX 670, such as the one we tested that can clock up to 1084 MHz, will be able to compete with the Radeon HD 7970.