That's the campaign, you can ignore it completely and do missions, discover planets and such.
I, for example, turned into a miner and set trade routes between planets, to sell the materials and make some quick cash to buy a better ship. Great times. GOG staff really needs to add Freelancer to the site.

Just to help in your search - as far as I can tell, it's 4X games you're looking for, not RPGs.

Not really. I'd classify games like MOO, Galciv, Civ as 4X, but not what I'm currently looking for (I don't mind games without the eXpand part)
That being said, there are some good recommendations here. Spelljammer is definitely a very interesting title (being able to bless your ship?! space mixed with medieval fantasy?! zomgz it's almost as interesting as ninja pirates).
On the topic of Freelancer, I wouldn't classify it as an RPG, but it's on my to-buy list because of the mods. I've seen some very nice mods that I'd like to try, and the game's pretty cheap now, so yeah I'm definitely going to get it someday

Clicky here, then.
Anyway, I think that space RPGs are under represented. I guess you could say that System Shock and System Shock 2 are sort of like RPGs, and Dead Space seems like a very linear RPG. Other than that, I think you'd have to travel back in time and play the old space RPGs, back in PC gaming's glory days.

Another old space RPG that might be up your alley would be Space 1889.
Of course, one cannot forget Ultima: Worlds of Adventure 2: Martian Dreams.

I recommend Freelancer too. It's a lot of fun, though it gets a little repetitive after a while.
Another great game that is similar is Darkstar One.

Escape Velocity: Nova? No stats, IIRC, but you upgrade ships, and some of the storylines are interesting. Trading, fighting, delivering packages halfway across the map before the deadline...
There's also the option to play the older Escape Velocity games as mods in EV: Nova.

There is also Space Trader:Merchant Marine. It's indie-ish, it's in space, and other stuff in space.

That's true. The scope of that game is immense - no limits bounded by the present game mechanics, you do whatever you want
msoya: YES! EV: Nova! I've had my eye on that one for a while. From the demo, it looks like it could be real great fun
Also, another nice indie game that I've found:
http://www.metalbeetle.com/spaceexploration/
The base game is free, but you have the choice of buying expansion packs or not. I'm guessing the core game is limited in content, but from what I've tried from the demo, it certainly looks potentially delicious

My advice is to push the IBM PC version aside and get the Amiga versions of the Starflight games instead. You get better graphics, better sound, and a better interface that way, and it's also much easier to emulate if you have the Kickstart 1.3 ROM (you need that specific version because they won't work with other versions).

Ah my demo of EV Nova expired and I never got a chance to explore a large part of it. Are the activities very routine? Is there anything interesting to do besides the standard fight/escort/trade? What kind of interesting storylines are there?

Kingdom Hearts has really impressive, immersive, realistic and spectacular space moments... nah... just kidding... ;p

Cast spell: resurrection 2015 :)

FTL! :)

NOW THAT IS WHAT I CALL A NECRO!