Once upon a time...
The storyline concept of RISEN is much closer to Gothic 1 and 2 than to Gothic 3. You habe a long and extensive first chapter chapter in which you explore the world and get to know the factions and people. The main story fades into the background in this phase and is only as present as necessary to help you understand the factions and the current situation on the island. Once you joined a guild, the story comes back into the foreground and begins to evolve.
Unfortunately, the subsequent chapters are kind of degraded so that you basically only deal with the main plot in the last chapters and have little else to do. This is a problem which was also present in Gothic 1 from 2001 and is intensified by the fact that the last chapter is very repetitive with basically only some search-and-collect quests. Hence, the only alternation comes from different scenes rather than innovative plot developments or social interaction.
Each faction has its own perspective on the plot and a lot of the replay value comes from these different perspectives. Since the game does not have multiple endings and always develops towards one single end, the differences in the last chapter are limited, of course. The most alteration is provided during the first two chapters.
By the way, RISEN cannot be compared to games like The Witcher or Mass Effect in that regard. It is based on an open world concept for players who like work everything out for themselves and resent to be kept on a dog lead. Only for the very first steps (during the tutorial), RISEN will take you by the hand and guide you safely through the plot. After that, you are on your own. Your next task is always very clear and you will not get lost in that way. But it is up to you if you follow it or instead go exploring or hunting, for example.
Nonetheless, Piranha Bytes could have done a better job in explaining the world they created to the player. Many thing remain unclear and leave the player scratching his head. What is the origin and organisation of the Inquisition? What is the history of the island or the kingdom to which it belongs? What is the purpose and role of the order of mages? These questions are not answered by the game itself. There no documents in the game which cast a light on certain aspects of the world. This is especially strange because the vulcano fortress with its large library would have been the perfect place to store a lot of book and documents on all kinds of topic. But many gamers will probably not be interested in that as long as they are kept occupied by the main quest. Which they will be.
There are several characters in the game which at some point or another will help you with certain tasks. Their help is welcome but most of the game's time, you play alone. RISEN is not a party based RPG. And the amount of help you get is much less than in Gothic 1 where the four friends helped to almost any dangerous situation like a deus ex machina. It remains open if at least one or two of the characters your grew fond of will reappear in a second part.