Well it also comes down to the graphics capabilities of certain laptops. Some gaming laptops have great graphics cards to handle the game, but most have either built in graphics, or weak cards like 8400-M etc. Laptops are not really meant for gaming even if they meet the requirements because of the power usage. Desktops can use high wattage PSU's to power hi-end graphics cards, where a laptop...well, just cant thats why laptops will never be the main gaming machine in PC land.
Your options would be to buy a gaming laptop from Dell or Alienware that can handle gaming. A buddy of mine has one from Alienware and can play most of todays games at decent speeds...although it cost him 3 grand for it LOL