The dual-core will definitely do better than the P4, and actually somewhat exceeds the minimum system requirements for Crysis. Since Crysis is more GPU than CPU intensive, you might actually get OK results with that machine. Just don't expect the world out of it.
And if you have the money, I'd definitely try to move up to a triple-core or quad-core for any serious gaming. You can do that relatively cheaply with an AMD build.