Did you play the console port of Risen?
I played the game on the PC. But I also bought the Xbox 360 version for when the day comes when we are all using Windows 382 and my copy of Risen won't work on the computer anymore without having to research day and night on the net how to get an age old game to work on contemporary hardware - I do this for my favorite games now, I buy a console counterpart when they're available.
I did fire it up on the Xbox 360 and played probably a good 10 hours. You are correct, the visuals and framerate are no where near the PC. At the same time, having lived through the era of Atari 2600 Pac Man, I could have still enjoyed the game on the Xbox 360, because my focus on gameplay is like a bloodhound's focus on sniffing out the bad guy… the gameplay elements that made Risen so fun on the PC are still there on the Xbox 360, it just doesn't look as nice and has much lower framerates, but still, imho, playable.