I am sure you've all stumbled upon game web sites that are made using Flash that replicate the old fashion arcade games, Nintendo or other game system games you played in the 80s and 90s.
Google's John Mueller said in a Google Webmaster Help thread that the vast majority of those sites don't really provide that much unique value. He said, "we often see "Flash-Games" sites that are really just a collection of existing games, that don't provide anything additional on their own." The truth is, most of those web sites have the same games as their competitors, just the ads are positioned in different places to try to enable an accidental ad click.
John's advice for new folks entering into the Flash Games area on the web? Build something more unique. He wrote:
If you're going to be active in that area, I'd really try to find something that can set your site apart from all the other ones, something absolutely fantastic that you've worked to provide to users, that isn't found on any other site.
Forum discussion at Google Webmaster Help.