When you say you have 8Gb of memory fitted.
Is it a single ram stick of 8Gb, or is it a matched pair of ram modules at 4Gb each Hardman. ?
Yes it will improve games, if you get any sort of brief lag while playing any game in question.
The more ram you have the better the system will run.
It will not improve the frame rate in games, but it will ensure games will run slightly smoother.
And besides as an example the new star wars rebel assault, or what every it was called recommended for optimal performance to run the game with at least 16Gb of system memory just a few months back when it was released for the Pc. Consider it a good investment because at some point quiet a few game coming out may require 16Gb of system memory in the coming months Hardman.
Anyway if you were running a single stick of ram also of 8Gb in size then your motherboard was running in single channel memory mode or 64 bits of data per memory clock cycle.
Where as fitting another matched 8Gb memory stick of the same brand and speed rating will use Dual channel memory mode that is 128 bits of data per ram clock cycle.
Double the data in one memory cycle Hardman.
Have a quick read by clicking on the link bellow.
https://en.wikipedia.org/wiki/Multi-channel_memory_architecture