Gaming on a laptop is a waste of money. For the same money, you can put together a good gaming PC and buy a laptop to go with it.
As far as gaming laptops go, there isn't much of a selection out there. The only thing that separates them from regular laptops is a dedicated graphics card. You won't get much game time on them since high end graphics use more power than even the CPU.
A tablet is more convenient and useful than a giant 17" laptop to lug around. I carry either tablet or ultrabook. They're not gaming machines, but I can still play games like counterstrike on the ultrabook. Most of the time I'll just play NBA Jam on my quad-core smartphone.