I'm not sure if I joined for any particular game. I just remember when they were still starting up and building hype, and they seemed to be promoting a nice selection of old school games (Fallout, etc). My first purchase that followed later on though was Giants: Citizen Kabuto. It looked like some silly fun.

My first reason for joining GOG.com was in 2009 when a friend sent me a message linking to the site for a free copy of the first two Tex Murphy games. I've written about my whole GOG history in more detail elsewhere in the forums so I wont repeat the whole story here, but that was my initial GOG game, followed by the other freebies in the catalogue over time.

My first actual purchase here was on Nov 17, 2012 and included:

UFO: Afterlight
UFO: Aftershock
UFO: Aftermath
American Conquest + Fight Back
Cossacks Anthology
Blitzkrieg Anthology
Blitzkrieg 2 Anthology

They were part of some promo deal and the UFO games looked appealing to me as they looked like they were inspired by the XCOM game franchise which I am a big fan of. The other games I had never heard of before but they looked and sounded like they might be fun and they were dirt cheap so I decided to give them a shot. That opened up the flood gates of my GOGging though and I bought 5 more games on Nov 21, another 5 more on Nov 22, and my addiction just ballooned outward ever since. :)

Far Cry.

Then I forgot about GOG for half a year or so, until I randomly checked out mid-2011 when EA came aboard. I discovered games I had never heard of before, like Crusader: No Remorse, so I stuck around to see what other titles I had never heard of appeared.

Now I'm invested, sort of.

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help bring bethesda and id or lucasarts

First purchase: Alan Wake.
Reason for joining: Giveaway of Fallout.

Reason for joining: the coming-out-of-beta publicity stunt that everyone hated. I had heard of GOG before then but never checked it out until I saw a few OMG GOG IS GONE WTF threads in a couple other forums.

First game: Arcanum for half off.

My first game purchased on GOG would be Sanitarium. It had very good reviews during its time back in the 90s, but the DVD was not sold here. Then when a local newspaper and online searches mentioned GOG and its collection of classic games and I found GOG had the game, I purchased it. The game works very well and I managed to finish the game with no problems.

I saw this site announced on the old Witcher forums. The DRM-free aspect caught my full attention immediately, so I headed over here and signed up. First purchase was Freespace and Freespace 2 on Sept 10, 2008... and I really should get around to playing them.

In late 2009, I had the urge to play Beyond Good & Evil again which I had rented on consoles when it was new. So I went looking for a copy. I didn't want the PC version since DRM, and I couldn't find a console copy in the few stores I checked. Can't remember how I stumbled onto GOG, but I saw they had BG&E and that everything was DRM-free. It wasn't the first time I'd heard of GOG, but it was the first time I had taken a close look at the site. Made an account, bought the game, and I think I'm up to 115 games now.

Free copy of Fallout 1. You can never have too many of those.
Stayed for the DRM free stance, and because games were cheaper, since 1$ ≠ 1€.
Even if a game isn't cheaper here (happens with steam sales), i still get it here.

Edit: First purchase was Hotline Miami. I could not remember and had to go and check. xD

My first purchase includes NWN and NWN2... i think it was a D&D sale on at that time.

But that really didn't bring me to GoG. I saw a reference to GoG in regards to Divinity Dragon Commander, and just started buying games i already owned or lost from the last 20 years or games that wouldn't run due to compatibility (Creatures) but work due to GoG's work... Some games although i have them are simply easier to use through GoG since patching was a pain in the butt...

The reason for joining... Pretty much DRM on steam which ticked me off....

First purchase: Fallout 1 on Jun 16, 2009.

Reason: I was looking around on an abandonware site for some old Sierra games I used to have. Saw a banner ad for GOG, checked them out, and was hooked instantly. Since then, I've digitally restocked all the games GOG has to offer that I used to own (and then some).

My first purchase, and the reason I signed up here, was Wing Commander: Privateer, on June 4th, 2011.

Rollercoaster Tycoon. One of my favorite games of all time. Played it a ton back when it first came out.

For whatever reason, a couple years ago I had an urge to play it again, but no longer had a copy. I looked for one used for a little while, before remembering that GOG existed. At the time I was a bit tight on cash, but I decided it was worth it anyway (bought it at full price). I did not regret my purchase, but I didn't buy anything more until just recently, when the summer sale coincided with me actually having money.

I first joined because of the free Fallout games. I came back when the gave away Dungeon Keeper for free, I bought Dungeon Keeper 2, and ever since then I kept buying more and more games. I used to play more on Steam, but once I realized that they used DRM and that I couldn't back up my game copies for future use, I moved to GOG. Thanks GOG for such a great service! I really hope to see many more games from my childhood here.

Hey! I also joined for the free Fallouts, we have the same avatar, and our usernames include the word "wolf" :P