Benefit of a 1-year MSc in Comp Sci in the UK
You didn't mention if you want to do an MS in the UK or the US. If the former, I have no experience of how it works over there. 

In general, an MS in CS does improve your chances of getting a decent job, but a lot depends on where you're getting an MS. In the US, the masters program is often viewed as a way to generate revenue via tuition, so your main benefit from the program is if it's very good at placing students. Obviously an MS from a place like Stanford or Berkeley will help you immensely because of the proximity of many tech options. But if you don't go to a place that has a good track record with placement, then the degree itself, while opening some doors, will not have provided you with maximum benefit for the price you're paying. 

Also, make sure you go to a place that has strong ties to industry in the areas you're interested in. Since you mentioned games, many universities (including mine!) have specialized MS programs in game design (and we have fairly strong ties to local industry in the game world). That might be too specialized for you, but you get the general drift