Probably the most important thing for playing games is the graphics card, and most laptops dont have a good enough graphics card for playing games.
And while nvidia do make graphics cards for playing games they also make "basic" graphics cards so just having an Nvidia graphics card in the laptop is not enough, it needs to be a "good" one, designed for games.
To be honest laptops are not the best thing for playing games on anyway, and a desktop PC, or a dedicated games machine like a PS3 or XBox is probably better.
If you do want to buy a laptop for playing games check on a dedicated gaming forum and ask for help there before making a decision