I think it would be a cool idea to have a suggested games list at the bottom of a game's main section that would essentially just recommend games that are similar. Not only would it help users find other mods that they generally wouldn't see, but it also might help creators broaden their content and move into multiple game sections and bring new content into a potentially empty or forgotten title. I figure it could be placed below the new and updated submissions that pop up on the main page.
For example, Counter-Strike: Source would have the other Counter-Strike releases there, but other shooters that are similar, like Day of Defeat or Insurgency. Perhaps it would be more trouble than it's worth to implement, but honestly I don't see anything negative from adding it.