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.