It looks like you're new here. If you want to get involved, click one of these buttons!
I'm a huge fan of these types of games, but I'm also their harsh critic. I hated Salem. Thought it was total waste of time.
Xsyon? Honestly it requires reading a wiki, just like wurmonline and mortal online. I'll go into depth later about my review, but as far as the "four sandbox games" go this game is right behind wurm online for best sandbox. Give it a go on the free trial server, you won't be pleasantly surprised, but you won't be totally disapointed either. Just save yourself the headache and have the wiki ready. I use two monitors for this ;P