Why does such a marvel of a game get this score?
You start as a shipwrecked nobody and work your way up, you have several choices on how the story unfolds and attempt to do well in challenging situations - you investigate, you fight, you bribe, you sneak, just deal with each situation your own way.
You are very weak when you start and build up your character the best way you can, trying to turn him into a powerful mage or a strong/skilled fighter, you get much stronger but not too strong and thus there is quite a challenge through the entire game.
If you've enjoyed the Gothic series I strongly recommend this game, if you're new into RPGs, I still recommend it.
I hope Risen 2 will be a masterpiece as well.