So why do you even bother replying?
I have not played Drakensang, but both Risen and Two Worlds are great games. Risen is a much more difficult game than Two Worlds and both are kind of.. quirky, so they demand quite a bit from the player. You will never be handheld in these games. You will get lost, you will get killed and you will fail quests. If you can live with that (and a rather low level of game polish), I'd recommend them both. Especially since they ought to be cheap now.
I haven't played Two Worlds (just seen it played by a friend of mine for.. like.. uhm.. I guess 2 minutes) but Risen seemed pretty polished to me. Not Bioware's level but except for a couple of dialogues with wrong names and a collision problem in a dungeon it ran almost flawlessly.
It also seems that they fixed these issues with the new patch.
Going back to the Drakensan/Risen/Two Worlds dilemma, I guess it depends on what kind of game you want to play.
Two Worlds seems more Oblivion-y with a much bigger world than Risen, lots and lots of objects (armor sets, swords) and things like that, don't quite know about the gameplay.
Risen is basically Gothic 2.5, its gameplay is a bit refined but otherwise almos identical to Gothic 1/2, the level of graphic detail is comparable to Gothic 3 which means a VERY nice world visually but... uhm.. 'wonky' characters.