A good gaming laptop will need a fast processor, plenty of RAM, good graphics card, and a large Hi resolution screen to enjoy the gaming experience. Typically all of this in a laptop is much higher than it would be in a desktop computer. You definitely will get more bang for your buck with a gaming desktop vs. laptop. Desktops are much easier to upgrade as well, which is important to those who are into playing the latest games.
It also depends on what games you are talking about. The system needs to be able to handle the basic system requirements of the game. That is a good place to start.
There are plenty of reviews and resources out there if you are interested in purchasing a gaming laptop.
Here are a couple of decent review or information sites:
http://computers.toptenreviews.com/gaming-laptops/
http://www.pcworld.com/reviews/collection/1659/top_10_power_laptops.html
You are probably better off getting a laptop that gets good reviews as a "gaming laptop" then you are trying to evaluate the basic specs on a laptop to discover if it would make a decent machine for gaming.
Good luck and happy gaming to yourself or the lucky gift receiver!