People who played this game also played...
When viewing a game, instead of just seeing how many people added it you should be able to see what other games those people added. For example a box on the side saying "Users who added Silent Hill to their list also added: Silent Hill 2, Silent Hill 3, Resident Evil 4, Outlast etc..."
This would be great for discovering new games from people who have similar taste to yours.
A big part of goodreads is it suggests material based off the things you've entered. I like the Walking Dead graphic novels, I should check out the Chew series, etc.. If I like some third person action games and haven't entered any of a certain series, suggest an entry or two.