It's hard but fun. You can't go wrong with gothic 2.
I myself are a bit new here also. And I mostly came here to buy witcher 2. but I got two freebies in a same deal 'cos my currency is euro. So I thought I take something which I had never even heard of. Well.. two worlds, that I had heard.. havent played yet and then enclave. and havent played. =)
I wonder would stonekeep would be good game. For me I mean.. when I have money, which is mostly never. And that arcanum seems interestings.. that looks like falloutstylish.

Edit: And Arx Fatalis is also quite good.

I second Arx Fatalis....great little RPG.

Yeah, DD is terrible for gaming addiction... I haven't even installed a few of my GOGs, (although buying BG2 before BG one was a little stupid.)

DK, PT, or WC Priv will do you some good. If you are into adventure games, you can't go wrong with the tex murphy series and I sincerely hope you also picked up Crusader No Remorse - I'm very much looking forward to Crusader No Regret when it is released.

RPG is first choice for me, but:

Psyconauts, Beyond Good and Evil, Sacrifice, all great.

Go outside your standard genre and then the buying purchases will spiral out of control.

Gotta buy them all.... That's my motto. Maybe we can make a flash based game where we take pictures of GOG's out in the wild... :-p

Planescape would be my top choice on your list, although the rest are great as well.. including gothic 2.

Oh.. and BTW... I own every single one you listed... so... good luck with that addiction.. lol....

A few from my own shelf to recommend:
Strategy:
Original War - a rather overlooked little gem which has you miromanage small groups of soldiers through a series of missions. No skirmish play sadly, but a good campaign mode and I think the MP world still has some life in it.

Stronghold series - without a doubt the GoG games that I have sunk the most time into - seriously if you ever liked castles and sieges this game gives you about the best you can get out there (excluding the Total War series - though even they don't let you build the castle). Stronghold original is best for its story mode, whilst the Crusaders is best for its Skirmish mode.

Sacrifice - hybrid first person RTS here, one of a unique breed of games where you run around with your army of fantasy monsters.

Arcanum - As big a rule set as DnD, a fantasy/steampunk based RPG game. I've honestly not sunk the time into this one that it deserves to really shine.

Ceaser III - slightly different strategy here in that its city building, a good challenge in learning how to build a working city, but also combines combat elements as well in some missions.

Alpha Centrauri - dispite generally being bad at the Civ games this one is a really fun title; light humour mixed with a tactical gem. A bit dated graphically, but the interface and overall menu controls are quick to learn and master and there is a great depth to the gameplay .

Yes, Arcanum is somewhat similar to Fallout (Actually it's better if you ask me, but that's just my opinion) Some of the quests have a lot of depth to them, and the rules are close to Fallout's SPECIAL system, with some twists (the whole tech vs magic thing, for example). Combat isn't that great though, but in turn-based mode it's tolerable.

If you liked fallout and enjoy steampunk/fantasy, Arcanum is definitely worthy of your time

Those that I played and can wholeheartedly recommend.

RPG:

The Fallout Saga (last one has less RPG elements and put more emphasis on tactical combat though hence the name...)
Ultima Underworld I&II (this one is GOLD, it's a must have)
Arx Fatalis (good game, spiritual sequel to the above)
Icewind Dale Complete (linear, but great story and action)
Planescape: Torment (very wordy, don't play if you don't like to read, but if you do, one of the greatest RPGs out there)
Neverwinter Nights (awesome)
Baldur's Gate 2 (the first one was practice, this one is gold... the sheer amount of subplots is mind boggling)


Strategy:

Age of Wonders (great strategy game)
Age of Wonders: Shadow Magic (pretty good too though I preferred the first one... this one is strikingly similar to Master of Magic in many respects and it made me wish they had taken more risks)
Disciples 2 (lost of RPGish elements too)
Jagged Alliance 2 (great if you love tactical combat, try the custom character generation form, you'll be in for a good laugh)
Lord of the Realms: Royal Edition (if you don't mind the dated graphics, the second game is pretty awesome)

try out Planescape Torment its good

I love GoG juss as much as the next guy, but I think you need to cool down w/the spending before you go broke. Unless of course you're a millionaire. Then feel free to ignore my friendly warning, which I do for your bank account, friend.

Why don't you juss try enjoying & exploring the games you've bought already? That way you won't burn out, and you'll get more out of the games you've purchased. I say this b/c I think the pace you're going at is based on the great emotions of joining GoG, at the expense of experiencing the true worth of the games you've bought. I could be wrong though. Maybe you can devour games like some book authors can devour books (ie- able to complete reading a novel in one day and say it was a fulfilling read).

All of my GoG purchases are for $5.99 or $9.99 (and I bought all on sale promos except one; and the free games, of course), but I treat all of them as if I bought them for $15.00 - $30.00, like what they were when they were first released on the market and then the depreciation a few years later. This helps me put in perspective the great games I have in my collection, enjoy them more heartily, and resist the temptation of buying every single game that they give a promo for which I only like a little, as opposed to whole heartedly.

Of course, everyone's mileage may vary. Juss tryna stop you from burning out & such. :OD

Edit: The Baldur's Gate series are my favourite games ever. I recommend it to anyone who has money to spare (without hurting your finances) & an interest in cRPG's.

And Planescape: Torment is another of my favourites, and it's not a game that you can simply breeze through. It's got a gripping storyline, and I've never heard of anyone playing & completing it in less than a week & finding it fulfilling in that way.

I have played it.. Well not in entirely through, it was years ago. But thinking about trying it again sometime in future. It was in my opinion better than baldur. But there's much to play and my hard drive is so small. =)

Welcome to GOG anonymous. I am very aware that I buy more games that I can play, but I do it happily. It's really not a big deal (I spend way more cash on beer than on videogames), and also I now consider GOG as part business, part Videogame Preservation Society. So I like to think of myself as a private donor.

EDIT: and about a purchase advice, it's as simple as this: RPG/TacticalStrategy -> Icewind Dale

Yeah.. With the beermoney I could buy lot's of games in here. (I was also a bit drunk here in gog-forum a while ago) Well, as said. There's plenty to play even with a few beers now and then.
And in rpg:s I always first go for a drink. Well not. =)