I think it would be amusing to have the ability to create personalized profiles with our own top 10 lists, favorite systems, etc. It's kinda fun to browse other people's collections, so being able to see personal details like that might be good. Then you could look up any random game and see how many favorite lists it's on for many people. Or use that data to create a section on the site that shows which game is on the most people's favorite lists, which games most people have, etc.
Or even a small comments board for each game could be fun too. All of us here love these games, and we like hearing about each other's experiences with them, right?