Steam was created to be DRM long before it was a digital distribution platform.

Of course Steam and GoG are competitors - there is no question in that. the differentiation (and the result would lead to your preferred supplier) is in how they market and to what segment.
Now we have to talk specifically about old games here since that is GoG's market segment and the only place the two actually meet in targets.
Sure Steam has a chat client in it's app... but I'd rather have forums I can search and I have found in general the GoG forums more polite than the Steam ones which is a win for GoG in my opinion.
Straight up dollar value games are cheaper on Steam in general for the same game itself - that is the game executable and any resources required to play that game. The old games on Steam are somewhat subsidised by the newer games for a given publisher. However given GoG's position is 2 price points with no game more than $9.99 we are talking about a few dollars different in the majority of cases.
Now lets make a small leap of faith. Lets say the game itself - the executable and any resources - cost the same. Now what does GoG add to that?
1) Pretty much every game in their catalogue has some bonus items - the quantity varies by game but the quality is invariably excellent. Steam has none of this.
2) Every game on GoG has been playtested by them from start to finish and they verify that it works on the modern platform. If there are any problems they will support the game sorting out mouse cursor issues with a wrapper executable and so on. Valve do not support the games. They are content delivery only. If it is broken it is not their problem and the publisher would have to do something if they felt like it.
3) There are no regional restrictions and no DRM. If you want to give your game away you can and you can safely recommend a game to anyone anywhere in the world and know they can purchase it. The Steam client is required to run any game from Steam and the Steam platform is well known for it's regional behaviour.
So that is roughly...
Reason Steam GoG
Cost 1 0
Bonuses 0 1
DRM 0 1
Support 0 1
You might say that the 3 dollar difference goes to providing all those winning points in a comparison......
And out of your annual gaming budget (or even monthly) how much is that 2 dollars or so really worth it to you? for me personally the amount of time I've spent posting in this thread I would have earned that at work and then some anyway....

to be fair there it was only really put into proper use at the release of Half Life 2. Yes that was used as DRM to not decode the data files till the release date passed but it was also Valve's foray into trying a digital distribution system for patches, games and so on. Store bought copies of the game were basically the files downloaded by Steam and still had to be decrypted on a valid Steam account....

Of course, the ENTIRE market of GOG is CONTAINED within Steam, save a small set of titles that arn't in high demand anyway.

The percentage is an ilustration. It's the VALUE that's the heart of Steam's supremacy (And that's what it is, supremacy) over GOG.

Interesting how people can see things differently.....
For me the VALUE of GoGs games are the ability to install anywhere with no net connection forever and a day, the extras like soundtracks they provide and the superlative support....
And for me that gives supremacy of GoG over Steam.
If you add to the fact they have stuck to their guns and never bowed to publishers on their core principles their morality/ethics is another reason for me to trust and purchase here over Steam.

The value of steam could be that the client saves games via steam cloud, accessible anywhere in the world and avoids losing saved data.
Steam Achievements, adds replayability to games.
Easily update system - updates automatically.
No need for a browser to access steam store.
Larger more active, more varying community.
Easy access to multiplayer.
Easy installs and downloads.
Accessability to information.
Good support(IMO)
Economies of scale
Larger games database(may even have a larger old games database)
Better marketing
Can play your games in offline mode without internet.
May help somewhat stem piracy to eventually bring game prices down.
Timely releases
consistency
and more.

It's really quite obvious.
One. If a company believes a game is worth more than $5.99, and don't get the option to charge more, they won't release it here. We all lose, not just the cheapskates among us (tongue in cheek, before you go nuts on me).
Two. If they add a $7.99 price point, that will quickly replace $5.99 as the "low" price point. It's still very cheap, and most publishers would gladly pocket that extra money while it would be very hard for any of us to argue (with a straight face) that an extra two dollars is too much to pay.
Three. The amount of copies sold during extremely popular sales can not be used as a measure of how well games would sell if they were cheaper in general. In fact, these sales have the worrying side-effect of reducing the perceived value of games to a level that may be too low to sustain independent developers.

Still, the developers need to add support for the achievements. That rules out older games.
Yeah. When they can be assed to put the updates out. When not, Steam just blames the developers, while the developers blame Steam, sometimes leading to games being unplayable because they lack critical updates. The same can be said about games that are not playable on newer systems - Steam does absolutely jack shit to make sure their games actually play. Case in point; Earth 2160, KoTOR.
Actually you do need a browser - IE. Steams browser functionality is basically just IE in a different shell. Removing IE entirely from your system results in the non-functionality of the Steam browser.
Translation: more retards. But I take it you like that.
Like so many other of your so-called value reasons, this only applies to newer games with proper Steam support built in. Older games may not apply.
For fuck's sake man. GoG has even easier installs and downloads. You can just download one single file (in most games case, sometimes 2-3 files), click on the installer, and you're done. You don't need to have the client up. Plus, you can choose to install where you like with GoG. With Steam you need to plan well ahead regarding the size of your install disk since it completely refuses to install anything anywhere else for all time thereafter.
I don't know what you mean by this, so I guess you're just making shit up. Do you mean the game forums? They're on GoG too. GoG even has it's own support section for each and every game, accessible after you've purchased said game. But since you haven't purchased any games on GoG, you're just here to troll and boast Steam superiority, I guess you wouldn't know that.
Shitty support(IMO). This is just subjective anyway. The actual fact is that their user base is so gargantuan they're not really able to give good support anymore.
Yes, Steam are indeed the Walmart of DD.
But Steam sells newer games also, and always has. Again you seem to confuse a large mass-market distributor with a smaller, niche one.
This is also some random shit you made up to sound cool and like you have a clue. You don't though, since the games released on GoG are a lot older, there's no real need for marketing them again. They were marketed when they were new. Aside from that, information and news about GoG is getting around in the exact same ways that information about Steam is. Via the internet.
I can't believe you brought this up. GoG games can be played in offline mode without internet too, you know. The fact that you see this as a plus is probably testament to how far up the DRM diarrhea dial you've travelled. It should be taken for granted that you can very well play your games wherever and whenever the fuck you want to.
This is also completely illogical. Steam does not in any way stem piracy. Every game released gets cracked and shared anyway, so how does Steam help stem piracy? It doesn't, really. About the only thing that stems piracy is to make sure the multiplayer portion of a game requires a valid copy to play. That way even pirates are forced to buy. Steam itself is just an abstraction on top, and people who are not inclined to buy games in the first place don't suddenly have a change of heart because of Steam.
Oh, GoG doesn't have that, do they? I mean, they've just been releasing over 2 games a week on average for the past one and a half years, and that's out of a predominantly niche market. Or; cry moar.
Again I don't know what the fuck this is about. I guess it's another one of those strung-up buzzwords you learnt in school this week? With regular forums columns, contests to win free games, usually releases every tuesday and thursday, and usually weekend deals every weekend, I say GoGs consistency is just fine.
Yeah, sure. It's like starting a complaints thread going "me, and many others". You know before reading that the "many others" part is complete bullshit. It's just you.

Sigh, I really liked games when they were replayable without achievements. Because you could have made lots of decisions actually changing what will go on. That was way cool...

I don't play for the achievements. Even in DAO its nice to pick them up along the way but I have not even tried to get even one.

Ah the memories of Deus Ex... still have my CDs knocking around but would love it on GoG hehe
And JacobNZ considering the so called points you brought up there in 'favour' of Steam.... well either you just don't understand what the GoG community and philosophy are about or you are just trolling at this point. Given the ample examples provided of where GoG differs from Steam to it's advantage and you ignoring them (the Steam cloud to download anywhere? guess what you can download anywhere with GoG too... you can even pop them on CD/DVD/USB so you never need a net connection again to install them nevermind play them) I assume that the latter is the truth.

Well you ARE the one trolling here, you should expect these kinds of responses. I know it's normal to troll on Steam forums, since it seems to be way of communication there, but we on GoG are much more old-school and simplistic.
I will give you an example, just so I am perfectly clear:
While on Steam forums, you say 'L O L, all you people playing old Fallouts are fags!' and get a reply saying: 'No u are a fag and a homosexual!' (I'm sorry, I can't speak that language properly)
On GoG forum, it's:
"I actually don't find Fallouts as great as everyone is saying. You see, I love RPGs, but postapocalyptic setting never really sucked me in, besides, I don't like combat system too much."
"Oh come on man, combat system ain't that bad! Fallouts were really rough at the beginning, and user interface is a bit clumsy. Maybe that's the reason you couldn't get into it? You migh consider giving it another shot, I assure you, it's worth it! Also, judging by the way you talk in other topics, and by your avatar, I can tell you are attracted to males, while being male yourself. Don't you want to go to dinner sometime?"
Now I know the latter is much longer and boring, but we got used to it and it's really hard to adjust, so we have created this little community here. See, I don't go to Steam forums, because I have hard time adjusting, maybe you should consider either not going here anymore, or try to adjust?

For the majority of games this is nonsense. Save games do not get uploaded to Steam servers so you will lose saved data if your PC dies. As for accessibel games the GoG games are accessible from any PC in the world at any time by signing in to your account.
Irrelevant. Games need to be designed with this in mind. The catalogue that we are discussing are old games.
Irrelevant. The catalogue that we are discussing are old games. There are unlikely to be any more patches for these and if there are any specific issues GoG provide a new installer.
Because the Steam client doesn't use the MSHTML DLLs and is so much more lightweight than a simple web browser.... GoG stuff is accessible from any browser on any operating system. I bet you could even download your catalogue with lynx or wget if you wanted to ;)
Larger is not always better - ditto for more varying. Pretty much everyone active here reminisces about old games and as a consequence is of an older more mature variety. Much more polite forums here than Steam.
If you are referring to the Steam Server Lists and chat clients then the games need to be designed with it in mind so irrelevant in the contexts of old games. The games that do have multiplayer here use whatever they were designed with in the first place. Old games on Steam have the same requirements for multiplayer gaming as GoG games.
GoG games are a single installer you download and then tell it where you want your game.... how much easier do you want it? Steam always installs games to it's install location. If you are low on disk space you need to delete games and then download new ones rather than just install to another drive - and no my full Steam collection will not fit on any of my disks.
Err.... not sure what you mean by this. Every game on GoG has it's own gamecard page where anyone can write a review. each game also has it's own support section and forums with the forums easily searchable....
If you say so... but then there are many horror stories on the Steam forums.... and Valve do not support the games just the content delivery platform. If there is a problem with a game and the publishers don't acknowledge it you are out of luck. GoG supports every game on here themselves - liaising with the publishers/developers themselves if the need arises.
Agreed. Steam has been around much longer and with their DRM policy and lareg install base they have the pull to get older games cheaply. If your only desire is to get a game as cheap as possible Steam will likely be your best bet. However as previously noted the difference is not huge since we are discussing old games and the GoG games have a lot of added value to them in the extras, no DRM and so on.
If we restrict ourselves to old games (leaving off good or not) the likelihood is that yes Steam has more games avaliable for purchase. But then HL2 which was the real start of Steam was released November 16, 2004. GoG has been around a little over a year. They had their one year anniversary only very recently. They are also somewhat more choosy over their catalogue - any publisher can't just pay a fee and have their game appear.
The games themselves do not need marketing as they are old. As for teh brand itself - well you found your way here ;)
I can't believe you wrote that as a plus for Steam..... Guess what? I can install from CD, DVD or USB on any PC without any net connection - never mind playing without one ;) GoG clearly wins out there....
Doing a google search for pretty much any game on Steam and the word torrent seems to make this laughable.... At any rate it is irrelevant as the market segment is old games. The price is already low..... The cost of brand new games is not in any way linked to GoG. Besides I had a thread about this only recently.... Go google for gog torrents if you want - you won't find many if any. The tight knit community here is a good one that wants to support the company. I would happily put safe money on the fact that GoG games are pirated less than Steam games.
Old games and new games usually each Tuesday and Thursday (or at least a nice surprise for us each of those).
??? Err every game has the same layout for gamecard, forums and support sections. Every game gets some kind of bonuses. Every game is playtested by GoG. To be quite frank I have no idea what you actually meant by this.
'And more' the last bastion of the unknown arguments.....

If they believe a game is worth more than $5.99 they can request GoG have it at the $9.99 price point.... If they want more than that for an old game they are being greedy and it's in GoG's best interests to stick by their philosophies and not be bullied by a publisher.
As for sustaining independent developers - given that GoG has a target market of Good Old games then I'm not sure that it is relevant in this context. Maybe in 5 or 6 years Introvision could be on GoG if EA/Activision haven't bought them ;)

This post needs to die.

That was too godamn funny.
I'm thinking now mods and stuff like that could come in handy. Stuff sucks here lately, and I would love to see a few users kicked from the forums to keep things respectable.