I hope they include some Infogrames games too, like Silver or Starshot, since Infogrames is bought by Atari, but I don't think so, At least not before May.
There are however some Atari games I'd love to see them working.
Ghostbusters: The Video Game is a new game but Atari blew it up with the faulty installer.
Maybe GoG can make it to work properly.
Asterix & Obelix XXL could be a good addition to Gog Atari line. It works only in some early versions of Windows XP (the ones without service packs). It doesn't work at all in Vista.
Getting Up: Contents under Pressure still works on Vista or newer OS but it was a great Atari game and it's a must in every collection.
Fahrenheit or Indigo Prophecy. A superb adventure game that I'd love to play again, but unfortunately that won't happen on Vista, unless GoG can do something about it.