Quotes that games do not work on Laptops are a little daft. I'm running on a not so new, but nice a powerful IBM ThinkPad T41p, just looking at some of the top sellers list at the moment I'll list the games that I have had no issues with what so ever.
Rome: Total War
Doom III
Half Life II
Star Wars: Republic Commando
Warhammer40k: Dawn of War
The Settlers: Heritage of Kings
Immortal Cities: Children of the Nile
Medal of Honour: Pacific Assault
Dark Age of Camelot: Trials of Atlantis and all free expansions.
Just to name a few of them....
The one that will not work
Star Wars Knights Of The Old Republic II: The Sith Lords
This has nothing to do with a laptop being used to play, but the quality of quality assurance testing that went into the end of the development cycle, or the lack there of.
Laptop V Desktop, power consumption is the only real deal here, the processor does not have hyper threading like the desktop, but a 1.7 GHz mobility chip will have almost the same performance rating, on core apps, as a 3 GHz, unless hyper threading is enabled. And for gaming, hyper threading adds next to nothing to the current generation.
Laptops do not have the same raw power, but in terms of performance per volt, they outshine all the desktops.