Tarque: Just to post an update: Now I own 184 games, including the free Battle Realms and SimCity 2000. I bought Banished and Legend of Grimrock II at the summer sale.
However, GOG lists 1125 games, so I only own 16,4% of all GOG games. When I started this thread, it was 17,5%... :)
Maighstir: However, in the catalogue, unbundled games are one entry, in the shelf, they're multiple. Your 184 games on your shelf might very well be 160 catalogue entries (I obviously have no idea what games you own, but if you own even one the unbundled ones, you will have more shelf entries than you own games from the catalogue).
Hmm, you're right, and I've got some of the "unbundled" games, too. So it's even less than 16.4%. Phew.
It should be possible to automatically get a key on GOG for games already owned on Steam (and vice versa), then I guess many of us would have twice as many games here... :)