Sounds about right.
Crysis is extremely... GPU intensive. There's another forum user complaining about 30fps at 1024x768 resolution on "Very High" with his ATI 5770 (which beats your GTS 250).
I used to play Crysis with an 8800GTS 512MB (2 generations before the GTS 250, but same GPU chip basically), also at 1440x900.
CPU Clock speed helps. I recall articles a couple years back about how being 3Ghz + helped with over all FPS.
Here's the thread I was mentioning:http://www.tomshardware.com/forum/290670-33-computer-crysis