What are the best laptops for gaming?

Games currently do fine with anything between 8 and 16 GB of RAM. 8 GB will be enough for most gaming needs while 16 GB allows extra leeway to run something memory intensive in the background or on a second monitor as well as future proofs the system, but even that can be skipped if the machine is used purely for gaming purposes.

It's also not worth spending more on higher bandwidth memory as increased bandwidth goes hand in hand with decreased latency to the point where they effectively cancel each other out performance wise.

As a general rule files read from solid state drives (SSD) will load quicker than files read from hard disk drives (HDD) so it's recommended for the operating system and software or games that are run regularly or can take advantage of the quicker load times.

For games the vast majority of computing will be done by GPUs. As long as the CPU isn't a bottleneck, GPU will define how performant is a gaming rig. So it's a price/performance evaluation. If you're willing to pay premium to get the best of the best, the GTX 980M is a clear choice. It's 20-30% more performant than the second best GPU, the GTX 970M, but the GTX 970M is a better deal overall. And if money is not a concern, it's even possible to put two GTX 980M GPUs in a laptop and connect them over SLI to almost double its performance. It has to be noted here, that some games don't have SLI support and will only be able to take advantage of a single GPU.

Most displays nowadays have IPS panels that for the most part offer accurate colors, great viewing angles and good response times. Still, there is a case to made for TN panels that offer better response times (2-3ms) at the expense of having washed out colors.

Current generation (Maxwell) GPUs are much better about heat than previous generation, while some current generation (Haswell) CPUs still can heat up. Next generation (Broadwell) CPUs are expected to address the issue of heat.