There are plenty of finished space-exploration games with very similar scope.

The Frontier series, for instance, featured a life-scale galaxy with seamless planet landing, each one entirely unique. It was released in 1993, and we're much better at making games like these now.

Here are some other games that will "never be finished":

- StarBound - http://playstarbound.com

- Rodina - http://elliptic-games.com/

- Elite: Dangerous - http://www.kickstarter.com/projects/1461411552/elite-dangero...

- Drifter - http://www.kickstarter.com/projects/celsiusgs/drifter-a-spac...

- Star Citizen - http://www.kickstarter.com/projects/cig/star-citizen

- Limit Theory - http://ltheory.com/

And there are still many more.