no easy way...
In linux mint 15 (before, I don't know), it seems that there are meta packages that include all default packages. They are :
for all distributions :
then depending on your environment :
you can first make sure those packages are installed, using :
$ sudo aptitude show mint-meta-cinnamon
and if need be installing them, like for example :
$ sudo aptitude install mint-meta-cinnamon mint-meta-codecs
To know if a package is a "default" package :
$ aptitude why package-to-test
=> if it gives you a package that depend on it, try again "aptitude why" on this package
=> if it shows you a package that belongs to one of previously given packages (e.g mint-meta-core for example), then this package comes from the default list
=> it it tells you "there is no reason for this package", then it means you can try to remove it (be careful !!! SOME packages must not be removed, such as linux-generic.)
Here is a method to clean your system from manually installed packages :
You can run a command that tells you what "manually" installed packages are on your system, on top of ubuntu default list. Manually installed packages are the ones that were installed on purpose, and not installed just because of dependencies (those ones are called "automatic"). Personnally, I made a script called "user_install" from the following command :
$ aptitude search '~i!~M(!~tubuntu-desktop!~tminimal!~tstandard!~tprint-server)(!~n^linux-)'
Now, the tricky part. try this command on a package that you do not explicitely want :
$ sudo aptitude markauto package-to-test
=> either the package is needed by another package (ultimately needed by mint-meta*, see previous step), and it will mark it as "automatic", without removing it. It will be removed from the list of "manually installed package" (see previous command)
=> either the package is not directly needed by any other package. In this case, it will ask you wheter you want to remove it... becareful here, as some packages (like icedtea-plugin, language-pack-gnome-en-base, mdm, linux-generic, mdm for example) are not needed by any one, but are important and should not be removed.