You do not need a powerful gaming computer to play older computer games on a ultrabook, iMac or other lower powered portable computer.
Sure, the latest VR titles with ultimate graphics settings are not going to run smoothly on a 15w chipset solution in an ultrabook, but said platform can properly accelerate older games like Counter Strike just fine!
Dedicated GPU Recommended for Gaming
If you want your laptop to pump the latest PC games with graphical performance that is worthy of praise, get a gaming laptop with a discrete GPU. The GPU does the graphics processing, and get one with at least 2GB of GDDR5, preferably 4GB and 8GB if possible! If you want a laptop that has awesome gaming performance, expect poor battery life, heavier weights and larger sizes.
Surprising Intel GPU performance!
Ultrabooks that have become common in 2016 will only properly accelerate newer games if you get one with a dedicated GPU with its own graphics ram. Somewhat surprisingly Iris Pro graphics on Intels 6000 series CPU's are actually equal to low-middle range discrete laptop GPU solutions, all while running at a lower TDP on die with the CPU, similar to the way that the Xbox One and Play Station 4 use a SOC with the CPU and GPU in the same chip package. These Iris Pro chips give ultrabooks moderate gaming chops while still returning much better battery life than gaming laptops with discrete graphics. Even middle range business laptops with a higher end Intel Chipset can perform decent with casual gaming!
Low End Laptop Gaming
One of my primary computers is a 14 Acer laptop with a 4200U low TDP integrated GPU chipset solution from Intel that actually plays "Dirt" a rally racing game via Steam with decent frames rates on moderate settings. To be more specific this machines CPU is a Core i5-4200 U with 2 cores & 4 threads that dynamically clocks from a base frequencies of 1.6Ghz up to 2.6Ghz with 3MB of smartcache, build on 22nm 3D Tri-gate Haswell tech that launch in Q3 of 13, running at 15w TDP max, the bus pumps 5GT/s over DMI2, while the 4400 series on package GPU with 20 cores that scale from 200Mhz to 1Ghz max, supporting Direct X 11.1, Open CL 1.2, and Open GL 4.0, it also features hardware decoders for Quick Sync and 4K video. This little beast is able to use a tiny 3 cell battery and still returns almost 5 hour of runtime on its two year old battery (non gaming- perhaps 2 hours of Dirt, though I rarely play it on this machine for more than 15 min. Haswell is known to "burn" up if you cook-em hot! This is not a gaming machine, but it can game in short burst with old titles on lower graphics settings!
Megs 13 iMac 27 and my 15 iMac 5K are similarly not gaming machines, but are more than capable of pumping older titles via Steam at lower settings. I have only tested the gaming power of these iMac, they are not meant for gaming.
Get a Console if you like Gaming
We game on an Xbox 360 and an Xbox One. I believe that gaming consoles are better for gaming than personal computers, especially if you are going to run a title like Destiny for hours at a time; I rarely play for more than 1 hour at a time. Consoles are purpose build gaming computers designed to play games. We are going to skip getting an Xbox One S, although it does make a compelling $250 UHD HDR Blu-ray player + more option. Project Scorpio is the 6 Teraflop beast console that Microsoft is currently developing and this is the one that Meg and I plan to replace our 2013 Xbox One with sometime in 2018-19 when the aforementioned Scorpio prices drops far below $499 with holiday sales discounts, like the kind you see on Cyber Mondays/ Black Fridays, etc!
Canon Lake to 10nm and beyond with Ice Lake
It will really interesting to see what kind of APU performance Intel is able to achieve with their next gen chip platforms. The 14nm process now very mature, the next gen 10nm process should offer better battery life along with improved GPU and GPU performance. The smaller node and new architecture combining to give more of everything good while using less power :) Performance per watt is a dominate mantra in the IC sector these days. Focusing on reducing power consumption is the key to building next gen notebooks with 16, 18, 20, 22 and 24 hours of single charge run time!