Make sure you have a good PC. I can play Witcher 2 on high, yet when I played Shogun 2 yesterday, it had constant framerate issues even on lowest specs. I dunno what was going on.
--
http://raptr.com/badge/cf898f37d9c30ef120ada6c35e636ad3/fs.png
http://myanimelist.net/signature/RyanSaotome.png