I'll defend the HW bg's too.
Do you know that it takes at least 3 or so weeks to create one background? Do you know how much f'n trouble went into making those backgrounds so SO pretty?
I will say this, the backgrounds were an INTEGRAL part in my first SP experience. If you look you can see the nebula getting closer and closer, until you're right in it. Afterwards the same goes for every other level, things get closer and closer until you're there. That's a nice touch on the dev's part, I was really pleased to see that much thought put into the creation of the backgrounds.
They give the game a 'feel' if I may say so. They add so much to the feeling of being in a large universe that's very colorful and alive. Anyway space isn't dead black you know. Just check out some of the Hubble telescopse shots and that new Shandra infrared one, nebulae and stars and whatnot are very colorful, down right beautiful if you ask me.