Rofl. You'll have to make it regular now!

Thanks to fronzelneekburm and congrats to the winners. I am glad it's over because it was driving me insane to try to figure it out!

I thought the "obvious" hint was the part where you said Thief Gold has been your favorite game for 15 years. That seemed out of place to me and I thought that was a hint which had something to do with "15 years." So I spent hours going through GOG, looking for games with 15-year-old protagonists or other 15-year-old characters or teenage characters. When those guesses were wrong, I changed strategies again, only to get more guesses wrong.

At one point, I was thinking about it so much, I woke up and got out of bed with what I thought was a brilliant idea: It must be Chronicles of Riddick! You like Thief so much, and Riddick also has stealth in it, and I thought you were dropping a hint about the mystery game having stealth elements when you said the obvious clue was "very, very well hidden." So I got online and checked the things which had become the standard first things I checked for any game: Was Riddick on the list of games you were trading? No! Was Riddick on the list of games which you don't already own and were hoping to get? No! Had you posted a review of Riddick? No! I was convinced it was Riddick at that point, but during the time I was checking those things, someone else had guessed Riddick! I thought, "Damn it all! I was too slow!" I thought the person who guessed Riddick would win. And then after all that, Riddick wasn't even the correct game! What a fool I was (and am)! lol

^ After the first two "hints" about specifically 860 guesses, and then the "red herring" about Day 1 purchases, I thought I'd figured it all out with The Witcher 3! There were 861 games in the catalog a couple days ago, and if you ordered them By Date Added, Witcher 3 was #861. I had some doubt, but still... you really could do the Enigmatic Hints now!

Thanks for the fun giveaway. Cheers.

I have to say, the theories you guys came up with are awesome! :)