What is a definition of an achievement? While Dungeon Siege is not on GOG, is it e.g. an achievement that your characters' titles keep changing the better they get in their profession (e.g. a melee fighter, an archer or a magic user)?
Are the extra tasks in GTA3 in-game achievements, like finding all the "hidden packets" and then getting extra weapons as a prize? Or are achievements something where you don't get anything tangible that is useful within the game, but just some title or badge?
I won't define the Dungeon Siege thing as an achievements system. As for GTA 3, you're talking about side activities which kind of resemble what achievements are, because they give you a completion rate based on a list of things to do, made by the developers. Usually I think of achievements as something like in Shadow Warrior 2013, where they are a mix or challenges, side activities, and they are not tied to the save game but they stack when you start a new game. However, achievements, when not platform-related (e.g. Steam or Galaxy achievements) are really arbitrary when It comes to defining them. There are also examples like The Saboteur (and, I would say, Batman Arkham Knight) where doing side activities and challenges gives you something within the game, but that's not mandatory.
thomq: Indiana Jones and the Fate of Atlantis
has what it calls an Indy Quotient (I.Q.) that is sort of like a score based on what is done in the game. There are three paths (Team, Wits, or Fists) and they sometimes overlap, so all three paths have to be done and everything in each path, in order to get the max total of 1000 points. In other words it's all optional, there are many ways to complete the game, and the score is simply a gauge of how much of everything has been experienced.
There's not a listing in the game itself of what gets scored and it never announces something was accomplished. The score itself is visible when pressing "i" to toggle from the view of the inventory to the score, so watching the score is possible if desired and therefore it's also possible to notice when something counts.
There is a hint book in the game goodies that lists everything that counts towards the I.Q. and their values.
That's interesting. It's tied to the save game, I suppose, but it resembles an achievements system in many aspects. I'll add It to the list and mix, it's cool to discover how many ways to keep track of your completion rate of side quests and challenges there were in older games. Nowadays it's all pretty straightforward.