not really like any of those,it is similar to gothic,if you played any of those?
It is 3rd person rpg,combat requires a lot of blocking,especially when going up against stronger opponents. It is about 50 hours for 1st time players also stars John Rhys Davies (Gimli-LOTR which is cool).
Not many weapons and spells though - that besides the lower budget(read as development time with regard to character animations and voice acting)of say Elder Scrolls is the only gripe I have against it.
Risen 1 is better than 2nd,because I loved it I had high hopes for 2nd and was let down, best approach for Risen 2 is to take it as a different game with follow on story.As far as number 1 being essential to playing number 2,somewhat for story,but basically in number one you meet a couple characters who follow through to number 2.
Elder Scrolls had many side quests,Risen has quite a few but they feel more with the story. I didn't play much of DA(got kinda bored with it)so can't really compare it.