I am currently playing Fallout 3 (again) on my Lenovo IdeaPad Y470 which has a Core i5-2410m CPU and nVidia GT 550m. It plays pretty well, the GT 550m is a pretty good mobile graphics cards. I would say it's an upper mid range graphics card.
I'm not suggesting you buy a Y470, just letting you know how the specs perform. You can read my review of the IdeaPad Y470 to give you an idea of what to look for in a laptop.
http
/www.tomshardware.com/forum/70694-35-lenovo-ideapad-y470-laptop-review