Handling of non-free non-redistributable data like shareware games assets are commonly handled by fragile shell scripts that involve wget, unzip, md5sum provided by the different distributions.

game-data-packager provides a way to share these unofficial packaging efforts in a central location; only a tiny part of this tool is distro-specific and is handled in a nice OO-model.

GDP has builtin support for the Steam & GOG.com online sellers and will also apply the patches needed by your games.

GDP would also fill a common need of upstream game engines providers that either have to document all the needed files: (like http://wiki.scummvm.org/index.php/Datafiles) ... or have to provide their own installer.