Withthe new Core i7 CPUs that just came out, they made one that can run crysis at a constant 60+ fps. It costs $9000, has 3 ATI Radeon 4870X2 in it, 12gb DDR3 RAM, and the CPU is clocked at 3.73ghz.
My computer, a Core 2 Duo, clocked at 3.66ghz, with 8gb DDR2 ram and one HD 4870, can run crysis with everything maxed at around 40fps during non fighting scenes, but drops into the 20s and 10s when they insane combat starts. I only spent $1300 making my computer, and I am more than happy with the results.