ktchong: It's no longer just "Good Old Games". I propose "Galaxy of Games" or "Galaxy o' Games", because of the upcoming GOG client.
As others mentioned, it stopped meaning "Good Old Games" a long time ago and GOG now refers to it as being just simply Gee Oh Gee, or just "GOG" pronounced "gawg" and no longer being an acronym. I do like the sound of "Galaxy of Games" though, it has a nice ring to it for sure. I doubt they will start to use a new acronym (backronym technically) in any official capacity, but the community could adopt one by consensus and usage perhaps. :)