Well I like the terragen render, it doesn't have to look exciting or flashy, I agree that the the sky and the space could be blended more.

The thing you need to work on most though is the space scene. It's too flashy, it's a bit bright, and there's too much happening. Dim it down a little, and it should look really good.

For just starting this genre so to speak, you're learning extremely fast. Keep up the good work man.