Spot on, although I must say that the better games I've played in the last few years happen to also be voxel-based. Could be coincidence.Zombies biting the player would be difficult to do, let alone in a MP game.
Ah yes, 7 days is a very generic zombie game with horrible graphics, yet we have outsold every truly generic zombie game ever made. I think your assessment of what makes a great game is spot off. Our game is flat out fun and has nothing to do with voxels, but good game design. There have been hordes of minecraft clones that all failed, if voxels were the magic secret sauce then the industry would have switched to them.
Space Engineers comes to mind. For all that the voxel-based nature of it gives a lot of flexibility, and designing ridiculously complex machines with the pistons and rotors can be quite entertaining, the game itself is missing elements that good games need. It could probably be made good but they don't appear to be trying to. Sad, really. The last couple of weeks my kids and I have been kicking the tires on Empyrion. I can see where they're on a trajectory similar to the Fun Pimps' 7 Days to Die...but they're arguably earlier on in the process so it'll be interesting to see if their product matures as 7 Days to Die has and continues to.