I have 65 games now and I'm sure there will be more. I'd love it if I could just make a script that executed the installers with a set of commands that tell them all to just install everything automatically and then exit.

Anyone know how?

Hmm... You want to install ALL games at once?

What you can do is install every game in C:\GOG\GAMENAME or something like this. Then just zip / rar the GOG folder. In the future, you can always extract every game or just the ones you want.

Although you will need to manually sort out the shortcuts after extracting.

-------- I understand that still is not what you're asking...

To solve this in the exact way you want, you'll need to install all games, and then make one big installer that will involve installing all games.

Is this something you're after?

It will require a little bit of work on your part, but AutoHotkey should be able to do what you want I believe.

And back up the GOG registry entries.

Hmm.. so far I haven't found that any are needed. Maybe The Witcher will need a key with 3 values (that's what the GG version needs at least), but other games I have function properly (even EA ones that come with SecuROM!)

gogwrap.exe's parameters are stored there. For most GOGs, that's needed.