Are you planning to use the display on the laptop by itself or plug in an external display? For any plans on using a large screen monitor you then have to look at what you will doing most of the time.
For gaming you will want to look at the higher end mobility models by NVidia or ATI for a start. NVidia has the 8800M series seen at
http://www.nvidia.com/object/geforce_8m.html
A review on the Diamaond Viper Radeon HD 3850 512mb model for laptops can be looked over at
http://www.hothardware.com/Articles/..._Ruby_Edition/