You can try http://www.exotica.org.uk/wiki/UnExoticA, wich has a lot (if not every) Amiga game music I need.
However, those musics are in custom formats, not exactly mods, but you can use Deliplayer for your listening pleasure. Better on a real Amiga computer or Minimig! 
many hundreds of the tunes are in standard mod format. This collection is for game/demo music but in the original format. Sound/Noise/Protracker were used for a lot of games.
also there is plenty of game music on modland
http://www.modland.com (also on ftp)
also many of the formats on modland can be downloaded as mp3/ogg recordings if you are on a machine that doesnt have a player handy.
