I wouldn't discard easily any of the series. I've made two playthroughs for Risen and i still have yet to finish Risen 2. Had 1 playthrough of Two Worlds and preparing for my second. Also, i really need to finish Two Worlds 2. So, as you can see, i liked both series for different reasons there.
The Voodoo specialization in Risen 2 it's very nice, but in the beginning seems a bit useless. And yet, it offers the most interesting aspect of the gameplay. The firearms are nice once you specialize in them, but the character becomes almost godly with them. Swords are offering the most challenging gameplay, but they are easy to find/forge.