Here's my impressions...
XS1: By and large an unremarkable game, but at least it was pretty easy to get into the gameplay. Just not particularly interesting even when you did.
XS2: One of those "doing what makes sense screws you over" games. Ie. I hated it since I never learned the counter-intuitive way you were supposed to play it.
XS3: Better than the previous two, but still not anything amazing. Pretty much a "vanilla" sort of RPG experience.
Sky Render - Sanity is for the weak.