Crysis in dx10 is very demanding, even my oc,ed 5870 wont get much better than 40+ fps @ highest settings. have you patched crysis yet ? Also I found with my 192 core gtx 260 setting up the nvidia controll panel towards performance helps some.
30FPS on Crysis @ Very High is pretty good - at 1920x1200 resolution, even an HD 5970 can't play all settings Very High with 4xAA. Your GTX 260 Core 216 seems to be performing as it should. Crysis was never nice on any hardware.