Someone already did, about 5 years ago. :)
http://gamesare.com/games/nothing/nothing.htm

I got 76 wishes fulfilled from 160 wishes voted for. I think that is a pretty good rate. There were some very nice ones added recently like Afterlife, Fantasy General, Worms World Party and all the Lucas Arts Games.
Not really but if you look at the wishlist it seems like it still lists all the games that were fulfilled, at least from the new wishlist:
http://www.gog.com/wishlist/games#order=votes_total

Does anybody remember the old wishlist? Now that was a mess.

The wishlist doesn't decide anything. All it does is give GOG's acquisitions department an idea of what they should look for, but in the end, it really doesn't matter what we put on the wishlist or how many votes it has, its all up to the rights owners to decide if they want to allow GOG to sell a game. We could have millions of votes for a single title and it won't matter because someone like Bethesda owns the rights and they won't sell their games here. At the same time, we could have a game with only a dozen votes, but because the rights owner is someone like Interplay, GOG has no problem getting rights permissions and they can easily sell it.

Right, we absolutely have to write developers a letter ;)

Did you see the "Completed" ones or not?