for gaming, the main strength depends on the gpu. the better the gpu, the better it will be at utilizing gfx components e.g. it's vram.
even for laptops, 1 gb gddr5 dedicated vram would be minimum for good 1080p gaming. make sure the laptop can handle the heat the gpu will dissipate. use a laptop cooler if necessary.
as for crysis 2, google 'crysis 2 benchmark for core i7 2xxxqm with <your gfx card name>'
and search tom's gfx card/laptop/video games forums.
gaming gfx card hierarchy chart (includes mobile chips):http://www.tomshardware.com/reviews/fastest-graphics-card-radeon-geforce,3085-7.html