The graphics card is the most critical component of any gaming machine; however, CPU and memory are almost as important and should be considered.
For a gaming laptop, a 16-17 inch screen size strikes a good balance between portability and having enough real estate to enjoy your gaming visuals.
Almost all gaming laptops have upgradable storage and RAM. Some models can have their processors and GPUs upgraded as well.
An ideal minimum to look for in a gaming laptop for modern titles is a 4-core CPU and 6GB of video memory.
Modern gaming laptops can be nearly as powerful as their desktop counterparts; however, there will be some sacrifice in performance per dollar. A gaming laptop should be considered if portability makes that sacrifice worthwhile.