is it every game? or just specific games? and are those games old?
the reason i ask is older games aspect ratio is 4:3 not the modern widescreen 16:9 so resolutions will always look odd/funny when you set the games to a 16:9 resolution.
what cables are you using to connect the gpu to the monitor, and would you mind filling out your system spec on the left hand side under your post count so we can have a badger (get it??) at anything else that maybe the issue.
oh and where are my manners, Welcome to the forum