It's Interesting, although it boils down to "the protagonist has been chosen by destiny", like in the Gothic series.
The island of Faranga is beautiful, there are quite a few memorable NPCs and the backstory is interesting. Also the 3 factions remind me of the 3 in Gothic 2, as in they are well fleshed-out and their motivations are believable.
Lastly there are a couple of interesting plot twists and various interesting side-quests.

Risen's storyline is fairly interesting and involves trying to discover the source of some mysterious storms around the island and the reason for why ancient temples have risen from the ground (the source of the game's name). As with Gothic II's ostensibly bland "kill the dragons k thx" plot it has various unexpected twists and lays a strong foundation for further games in the Risen universe.
As with the Gothic games--with the exception of Gothic 3, which didn't use chapters--you will spend a huge amount of time in Chapter 1 with a ton of side and faction quests to take on, almost all of which have multiple solutions. Chapter 2 is a bit shorter, as usual, but is still rich with things to do and many new places to explore.
The last two chapters (it has four rather than the previous standard of six) are more combat-oriented, and you will spend a lot of time performing tasks to advance the plot rather than doing optional things on the side. There are only a couple of new side quests in these chapters. Side quests you didn't finish earlier remain available, however, so if you didn't do them all early on you will still be able to enjoy some variety throughout.
As in the Gothic games additional enemies spawn throughout the island with each new chapter, so there is always something to do. The revised magic system allows you to make various scrolls out of the appropriate monster trophies (teeth, wings, etc.) so hunting enemies has an additional benefit. Scroll making is by no means necessary to get through the game (you can find or buy all the scrolls you will need), but it's another great thing to experiment with to give yourself an extra edge. The same goes for the excellent alchemy and forging systems.

Alright, I'll try the demo out and see how it is.

Not if you mod Oblivion, the user created mods make the game epic.

Risen is an excellent game.
Gothic 3 is good if you apply the CP 1.73 patch the texture mods. Looks and plays a lot better!