Crysis will no doubt be a fairly demanding game. It will require a good system to perform well. However, CryEngine2 is very scalable so lower end machines will still stand a chance. Here are the official, and complete system requirements for Crysis.

                                                                             
                                                                          Crysis
                  Minimum System requirements
                CPU: Intel Pentium 4 2.8 GHz (3.2 GHz for Vista), Intel Core 2.0 GHz (2.2
                GHz for Vista), AMD Athlon 2800+ (3200+ for Vista) or better
                RAM: 1GB (1.5GB on Windows Vista)
                Video Card: NVIDIA GeForce 6800 GT, ATI Radeon 9800 Pro (Radeon X800 Pro for Vista)                 VRAM: 256MB of Graphics Memory
                Storage: 12GB
                Sound Card: DirectX 9.0c Compatible
                ODD: DVD-ROM
                OS: Microsoft Windows XP or Vista
                DirectX: DX9.0c or DX10
                  Recommended System requirements
                CPU: Core 2 Duo/Athlon X2 or better
                RAM: 1.5GB
                Video Card: NVIDIA 7800 Series, ATI Radeon 1800 Series or better
                VRAM: 512MB of Graphics Memory
                Storage: 12GB
                Sound Card: DirectX 9.0c Compatible
                ODD: DVD-ROM
               OS: Microsoft Windows XP or Vista
               DirectX: DX9.0c or DX10