It would be great if it was something like PCEDaisakusen.net where when you click on a game, the information (year released, screenshots, general info, reviews, etc.) is contained therein, along with the names of other people who own the game, to give an idea of rarity
Example: a list of NES games, you click on "kung fu." On the page that comes up, you see screens, box art (front and back), year of release, etc. halfway down the page, theres a "user rating" (the average of all the users who have rated the game), and any reviews that people have written up.
What works for one system-specific site, may work for something ike this as long as all the information is organized. i for one would love to have a centralized place in which to keep track of all the games i own. especially if its a site im going to visit often