As a side note for the Steam games, on most modern titles Steam also backs up the saves to the cloud now automatically. So with the newer games just reinstalling under your account will have the client fetch the saves for you.
It's one of the neat little things they implemented quite recently.
If you have a download cap on your internet then get an external hard drive and back up the Steam games too. Steam has this feature, that way all you'll have to download is any updates.