I think that it was a good idea for Ironclad to not have a campaign for Sins launch, but I am glad that the expansion will have one. I think that in this way players focused on the Mulyiplayer and could play the game without having objectives that would restrict them. In my opinion, Sins feels like a game that needs a campaign. Each race has so much lore and backstory that I think Ironclad would have cheated us if they didn't make a campaign for it (besides it would suck never knowing who is after the Vasari).
There is a semi old game (it came out around 2003 or 4ish) called Universal Combat, and it didn't have a campaign. I HATE that game. You got to pick a class, Commander, Fighter Pilot, Marine, a few others and a race then the game set you up on a planet or in your star ship and you then had free reign. No direction what so ever. The manual said you could make up your own story, but all I got out of commanding a star ship was blowing up enemy ships. I dont even know why they were my enemies! I got boarded by hostiles every time a ship appeared on my radar for a second even when I was in warp. The whole point of my rant was that the game didn't have an actual campaign, you pretty much had to create it yourself and it sucked.
Now on to Galactic Civilizations 2, I LOVE this game and I've never played its' campaign mode. Gal Civ doesn't need a campaign for you to love it (that may be because it is like the Civilizations series, empire builder). Lets say you start out in the center of a Huge Galaxy map with 8 other civilizations, you could decide that your empire is going to be evil with the idea that it is the center of the galaxy and you want to expand and conquer the other races. Wha La! Your personal story is set and it will be different every time you play, but it doesn't get boring.
Another game I like is Supreme Commander, it has both campaign and skirmish. Once I finish the campaigns I will probably play a freak load of skirmish maps with AIs and kinda make up a story as I go along.
Some games need a campaign and some games shouldn't have one, other's are perfect with both. I am glad Sins is getting one, but for now I'll make up my own story.